[SOLVED...] X3 isn't handling my large session (52 tracks, 1hr 22mins, avi)

[SOLUTION] {
1. Save As... with "Copy all audio with project" and "Create one file per clip" checked,
OR
2. Wait. It appears that X3 needed time to process all the clips in the session (1800+). After a...while...the session ran like it was supposed to. And in fact gets going just a wee bit faster than X2 (X2 seems to open a default screenset then changes to the one I last had, which takes a moment; X3 goes right to the appropriate screen configuration)
1. didn't take as long to do as 2., but with 2. I get the full clip that I can still edit if I hosed it up, so: yay.
}/ end solution...I now return you to your original post...
 
I am getting start/stop latency with X3- lots of it- that I am not getting with the same file in X2.
Project contains a 15GB avi (1hr 15min  and 22s) file, 52 mono tracks, but no more than 12 playing at any one time, plus the original stereo audio track of the avi file.
I originally had 8 Sonitus compressors, and 2 instances of Prochannel's EQ, but all FX have been deleted and FX disabled.
 
1. When i press play, the video and sound playback  start, but the Now Time/ Now Time Marker nor any level meters work (this is intermittent as sometimes the Now Time and level meters work).
2. The Hard drive in running continuously.
3. When I press stop, there is a 22 second delay before playback stops. Sometimes. Sometimes it stops immediately
4. There is a further 16 second delay before I can do anything with X3, as the "I'm doing something" mouse icon is displayed...because apparently X3 is doing something. And that's IF X3 understands that it's supposed to stop. There is ALWAYS this minimum 16 second delay after playback stops. Sometimes the "I'm thinking" icon goes on for longer.
5. The "thinking" icon pops up randomly even when the transport is idle.
6. This behavior happens regardless of whether the thumbnails are displayed or not.
7. This behavior happens after deleting the video, saving, and restarting X3.
8. The session works fine in X2, even after opening the X3-saved file in X2. 
 
X3 isn't crashing or white-screening, but apparently it can't handle this project like X2 can: it's the same file with the same plug-ins.
 
On the plus side: my music sessions seem to be working fine in X3.
 
Win7 x64, 12GB ram, 64 bit X3a and X2a, NVidia GeForce 9400GT, i7 920 @ 2.67GhZ

That's a pretty big file for a 1:15 avi - I'm betting it's either MPG-2 1440x1080, or MPG4 1920x1080....
 
Normally in such situations, I would make a low-res proxy avi in order not to tax the CPU. Final Audio can easily be mated back in a video editor.

It's a 720x480, 29 frames/second, 48kHz stereo .AVI, rendered via Adobe Premier Pro (other settings unknown at this time)
Problems persist with or without thumbnails 
The problem persists after deleting the video entirely 
The problems persist after archiving the video's audio.
I could possibly decrease the video resolution but I'm doing ADR and Foley and that defeats the purpose.
 
I'll stick with X2 for this project, I suppose, as X2 is working just great. But I could really use the comping and track lane features of X3.

Tom Riggs
I had a large project that was having trouble too until: I checked the preferences for sync and caching and enabled the disk read caching option and upped the cache size to 1024.
You have to click the advanced button at the bottom of the preferences window to see the sync and caching options.

+1 tom, these settings do not get migrated.  i had the same issue from x1>>>x2.  52 audio tracks i would recommend 2048.  

15GB is more than a little unusual for 720x480, regardless of codec. A 720x480 (3:2 or 16:9) DVD, which must be encoded with MPG-2 tops out at 8.9GB. That's pushing a lot of data for its dimensions. An hour of 720x480 in presentation format (as on a DVD disk) is lucky if it hits 2 or 3GB.

Videos get big like this when encoded with a lossless or 'visually lossless' (i.e. Cineform, DNX..) intermediate codec, which is great when multiple codec passes is needed, but doesn't help any at all when scoring. 
 
It is interesting that that X2 is working better with that file. It might be that changes in X3 do not allow such large caching as would be required that file. I'd stick with X2 for now - deadlines are deadlines. But I'd still have point out that it's far better to score to proxy files, they're nice and small and they don't get in the way.
 
Cheers!
 
 

SuperG, you're right it's a big file, but the person doing the rendering is technically unsavvy so I havent been able to get a happy medium of quality versus size (nor had the time to re-render the file before having to record...so it was a good thing X2 fired right up a couple of weeks ago when it had to). However, it doesn't answer the question of why I am still getting the problems after deleting the video, so until  otherwise informed, I am going to assume/believe that X3 needs to re-write (for lack of a better term) all of crossfades, slip edits, and other clip/track data, because Saving As... to another folder and saving the clips with the session as new clips fixed the issue.
In fact as we are done with the ADR, I'm going to re-render the AVI  and see if that helps.

Oscar, I know you're busy...
 
Just trying to help. Let's us know how the re-render goes.  
 
 

Allllllright: the original file is working now. On my break [Bwahahahahaaaa: break!] I mucked about with the original X2-to-X3 file. I believe my hypothesis to be correct : the number of clips was taking X3 an inordinate amount of time to make the X2-created file into an X3-friendly file (Bakers want to respond? Am I off track?).
So I can be happy now. Are you happy? I'm happy. 
 
SuperG: I appreciate your knowledge, I just wanted you to know how I got where I am on this. 
 
Again, thank you everyone for your assistance. Now: to really screw things up and actually start mixing and Foleying (in the audio sense, not the medical sense...ew) and adding Perfect Spaces and Compressors and ...  
I'm going to see what X3 can take!