FCPX Playback head slow in timeline? Using Proxies.

Question

Im editing 5k footage shot on the Red Epic.  I have a interview laid out in my timeline (or project) and I am going through and setting my "IN" and "OUT" marks and cutting using "APPLE-X".  Also using "J" on keyboard to rewind to certain points where I want to mark my "IN" points.  The footage runs great until I start cutting frequently.  My playhead starts to be slower than the actual video playing back. So when I make my "IN" and "OUTS"  and then cut, my edit is about 6 or 7 frames off.  It seems as if the playhead is lagging or it is slowed.  Every clip is converted to the 1080 proxies.  I am not mixing footage formats.  Im editing with the proxy setting enabled.  I am cutting from a GTECH Firewire 800 Drive.   Here are my computer specs:
MAC PRO:
MAC OS X 10.6.8
Processor: 2 x 2.93 GHz 6-Core Intel Xeon
Memory: 32 GB 1333 MHz DDR3
GFX: ATI Radeon HD 5870
Final Cut Pro X 10.0.6
Please let me know if you can help me.
Thanks
Elliot Pollaro

Answer 1

be sure there isn't anything else accessing your drive....file downloads....email auto checking...etc.
try seeing if the behaviour changes by alternating the preferences for playback, best performance vs high quality.
it's hard to understand why this would be an issue with proxy footage. enable the checkbox to warn you when drop frames occur. just to see...
does this only happen when editing 5k footage or can you reproduce it with other footage?
is it a fast 7200 rpm disk? might it be too full?
because you're using proxies, it sounds like something is slowing the hard drive down such that it's not accessing fast enough.