Acrobat 9 Pro very slow open files over network in Windows 7

Question

I have installed Acrobat 9 pro on my new PC. It's running Window 7 64bit. I use it for pre-press of high-resolution files for printing. Sometimes the file sizes run into the 100s of MB.The new PC has reasonably high specs, with 6Gb of RAM and a 2.8Ghz Quad core i7 CPU and gigabit networking.
Opening them when on the local hard disk is reasonably fast. For example a multi-page 400Mb file starts drawing the first page withing 3 seconds. But opening the same file when it's on the server of our gigibit network generates a very long pause. The application locks up and dispays a "not responding" message for 2-3 minutes. The bigger the file, the longer the pause. It doesn't completely crash -- eventually it starts to draw the pages and I can work as normal.
I used to have Acrobat 9 pro on my old XP PC which was a cheap low-end machine when bought 3 years ago. (has on-board shared RAM graphics card and only 1Gb of RAM). But what grieves me the most, is this slow old machine will open the same 400Mb file off the server so much faster than my expensive new machine. There is no lock up and it begins drawing the first page after only approx 5 seconds.
The problem doesn't seem to be simply related to slow network speed. I can copy the entire 400Mb file from the server to my hard disk in only 12 seconds. The old PC is actually slightly slower copying to/from the network. If the application was for some reason copying the entire file into memory or to a local cache, this should still only generate an extra 12 second delay -- not 3 whole minutes.
Adobe Reader 9 doesn't have the problem. I can open the 400Mb file off the network on either my new or old machine within seconds.
Acrobat 9 Pro doesn't have the problem on an old G5 mac either. It's somewhat slower than my old PC but will begin drawing the first page after a few seconds,
So what exactly is Acrobat doing for those 2-3 minutes?
I have already tried:
1. changing network ports/cables.
2. disabling anti-virus software
3. disabling "remote differential compression"
4. Patching Acrobat 9 to 9.2
5. Files located on Windows servers and Mac Xserves.
Not improvements from any of these.

Answer 1

I think I have isolated the source of this problem. It's the Pitstop Professional 9 plug in. I un-installed this, and everything opens quicker than greased lightning. I re-installed it and it's back to slowsville.
Unfortunately Pitstop is essential to my workflow.
Until recently I did my pre-press on a Mac G5 with Acrobat Pro 7 and Pitstop 6.5. I never had this problem with slow file opening. But it seems that the delays would occur when I used the plug-in with large complex files.. So it would open files as fast as you'd expect from an elderly machine. But starting to use Pitstop would result in a prolonged period of staring at a spinning beachball.
I wonder is there any way to stop the Pitstop plug-in from initializing until it is used? So the plug-in stays inert until you select the tool from from the menus.