Ongoing problems with newest Mac Pro and CS4

Question

Hi all,
I've just switched from a Final Cut Pro editorial house to a new company that bases production around the Adobe Production Suite using Premiere Pro CS4 for all our editing needs. From what I understand about this company (and this workstation) is that Premiere Pro CS4 has been buggy on this machine and this machine only. I find this strange as it is one of the newer high end mac systems available right now and is more than capable of crushing most video that will be put into it.
In brief a summary of the problems include;
1.) Final exports rarely work, no matter the codec, bit rate, size, duration, etc.
2.) If AME CS4 does manage to successfully export a piece it will generally have random black frames right at every cut starting about halfway through the piece.
3.) Even so much as switching sequences within a project manages to bog the system down and crash it, thus making me have to force quit the program and occasionally restart the machine.
4.) After rendering the work area the machine suddenly becomes unresponsive and thus causes another crash/force quit scenario.
5.) Certain audio tracks will play for about 2min and 30seconds and then mysteriously go silent, while a clear and present waveform is able to be seen (however occasionally premiere will cut this part of the clip off!)
I will post the hardware and software specs below but I feel it is necessary to detail why I find these problems to be extremely peculiar.
Firstly the projects we have are generally shot on the 5D MkII. I understand CS5 has the ability to play these clips back through it's mercury playback system (after it's own internal conform) at real-time and allow you to edit as if it had been transcoded traditionally. We are planning on obtaining a copy of CS5 in the near future but I am currently worried if these problems may be associated to faulty hardware.
Upon my arrival I formatted every drive and did a clean install of OSX Leopard 10.6.5 as well as a fresh install of Adobe Production Premium CS4 (updated to most recent release). This leaves out any possibility of a plug-in such as the red giant filters or sapphire filters interfering with the rendering and exporting process. Nothing seems to work. Even throwing an uncompressed 8-bit clip into AME CS4 manages to crash it.
A coworker of mine had two great ideas on the problem the other day for me to test out. The first being that it could be a bad piece of ram. I figure this could be a possibility as I don't know the history of this machine and I noticed all the RAM slots are full of 1gig sticks (and two 4gig sticks) so there could be a bad one in the bunch. I went through the process of elimination leaving one stick in at a time and testing an export (extremely time consuming) and every time it failed. His second idea was to take my project file and associated media to the creative directors computer which happens to be a two year old Mac Pro running CS4 (on OSX Leopard). He has several plug-ins installed along with tons of additional applications etc etc. Sure enough I loaded up my project file consisting of a bunch of 5D MkII footage and it played back perfectly, exported perfectly, tabbed through sequences perfectly, and did everything it should!
My question is why. Why would his older machine work with this footage on the same version of Premiere Pro CS4 and not my newer, faster, shinier editing machine? I've done everything I can to test any theory I've come up with both from my own experience as well as through internet research. Deleted PList, emptied RAM, emptied Cache, reformat and reinstall, swap RAM around, tested different hard drives, etc. The problem is not isolated strictly to the H.264 files the 5D MkII produces either, as even the uncompressed 8-bit files I've brought in won't play nicely with the system either. It's such a bummer that my first experience with Premiere Pro had to be on a machine that has these horrible quirks but I feel it has a lot to bring to the table over Final Cut Pro and I would love to find a solution to this problem so I can get back to cutting!!
Thank you in advance for all of your help!
System Specs (Hardware)
-Mac Pro 5,1
--2 x 2.93 GHz 6-core Intel Xeon
--14 GB 1333 MHz DDR3(all tested OK)
--ATI Radeon HD 5770 (also tested with a new nVidia card as well)
--(Internal) Operating System Hard Drive - 250GB 7200 RPM
--(Internal) Project File Storage - 1TB 7200 RPM
--(Internal) Preview File Storage - 500GB 7200 RPM
System Specs (Software)
-Mac OSX Snow Leopard 10.6.5
--QuickTime X v10.0 (118)
--QuickTime 7 Pro v7.6.6 (1710)
---QuickTime Version 7.6.6 (1756)
--Adobe Premiere Pro CS4 v4.2.1 (003 (MC: 166418))
--Adobe Media Encoder CS4 v4.2.0.006
Example Sequence Settings and media for a usual Project File
-Media
--24GB of 5D MkII footage (1920x1080P 23.976 frames/second H.264 files straight off the card)
--2GB of sync sound (.WAV)
-Sequence Settings
--Editing Mode: Desktop
--Timebase: 23.976 frames/second
--Frame Size: 1920 horizontal 1080 vertical 16:9
--Pixel Aspect Ratio: Square Pixels (1.0)
--Fields: No Fields (Progressive Scan)
--Display Format:24fps Timecode
--Audio Sample Rate: 48000 Hz
--Display Format: Audio Samples
--Video Previews File Format: I-Frame Only MPEG
--Codec MPEG I-Frame
--Maximum Bit Depth (Unchecked)
--Maximum Render Quality (Unchecked)
Adobe Media Encoder Export Settings from Uncompressed 8-Bit FILE to High Quality H.264
-Source Clip: Uncompressed 8-Bit 4:2:2, 1920 x 1080 Millions, 16-bit Integer (Little Endian), Stereo (L R), 48.000kHz 23.98, Data Rate of 799.15 mbits/s.
-Format: H.264
-Preset: HDTV 1080P 24 High Quality
--Customized to:
---24fps -> 23.976fps
---Pixel Aspect Ratio: Widescreen 16:9 -> Square Pixels
---Bitrate Encoding: VBR, 1 Pass -> VBR, 2 Pass
---Source XMP metadata turned OFF
Adobe Media Encoder Export Settings for Premiere Pro SEQUENCE to High Quality H.264
-Source Sequence: See above example.
From AME Directly: [File>Add Premiere Pro Sequence>Project>Sequence>OK] (Usually takes a long time to get Sequence section to show up)
From Premiere Pro: [File>Export>Media]
-Format: H.264
-Preset: HDTV 1080P 24 High Quality
--Customized to:
---24fps -> 23.976fps
---Pixel Aspect Ratio: Widescreen 16:9 -> Square Pixels
---Bitrate Encoding: VBR, 1 Pass -> VBR, 2 Pass
---Source XMP metadata turned OFF
Adobe Media Encoder Export Settings for Premiere Pro SEQUENCE to Uncompressed YUV 8 bit 4:2:2
-Source Sequence: See above example.
From AME Directly: [File>Add Premiere Pro Sequence>Project>Sequence>OK] (Usually takes a long time to get Sequence section to show up)
From Premiere Pro: [File>Export>Media]
-Format: QuickTime
-Preset: Custom
--Customized to:
---Video Codec: Uncompressed YUV 8 bit 4:2:2
---Quality 100
---Width: 1920 Height: 1080
---Frame Rate: 23.976
---Field Type: Progressive
---Aspect: Square Pixels (1.0)
---Render at maximum Depth (Unchecked)
---Audio Codec:Uncompressed
---Sample Rate: 48000 Hz
---Channels: Stereo
---Sample Type: 16 bit

Answer 1

The move from FCP to PP is a good one, however, it's only half way there.
Next, move to a Windows 7 64 based machine using an i7 950 and 12 GB RAM at a minimum (with a GTX 460 or better as a seriously considered option), and then upgrade to CS5.
Chances are more than excellent that doing will resolve all your issues.