We need to know a lot more if we're going to help you.
What exact version of After Effects? Have you installed the recent updates ( http://adobe.ly/lsrkmJ )? What operating system? What kind(s) of source footage? Has this ever worked before? What other software are you running? Do you have any third-party effects or codecs installed? Tell us about your computer hardware. Are you rendering with OpenGL? Are you using Render Multiple Frames Simultaneously multiprocessing?
Oh wow, ok here we go.
Running Version 10.0.2.4 on a dual booted Mac (using the Mac side)
OS - OS X v 10.6.8
2 x 2.26 GHz Quad Core Intel Xeon - 16 GB RAM 1066 MHz DDR3
The file wouldn't even open when I switched to the PC side which has vista I think, but I'm not positive.
Had Photoshop CS5 open, have 3rd party plugins and codecs installed but aside from Particular 2 I'm not using any in the area I'm trying to preview.
Not using multi processing or render multiple frames. Using a 2048 X 1152 size (this was comped then scaled down to 1920 x 1080) quicktime at 23.976 for just under 36 seconds with an Animation codec.
Was ram previewing the area I wanted, earlier in the day. It all of a sudden just started crashing when I tried previewing at all in this file. Went back to the last version I saved last night and it ram previewed fine.
I checked for updates in Help - Updates and it said it was completely updated.
Sorry about not including this earlier.
So it's working fine now?
If you get it back into a bad state, please file a bug report. You can't attach a file to a bug report, but the person who reads the report may respond to you with an email address and a request for the project that is showing the crash.
Wow, actually. Yeah it is working fine now. I don't even know what magic you just did but it worked.