I have Version 10.0.1.19 running on windows 7 64bit with 8Gbs of RAM. Everytime I try to add a timecode effect to a wmv and export the file After Effects crashes half way through export.
Install the CS5 (10.0.2) update and try again.
Has this ever worked before? What other software are you running? Do you have any third-party effects or codecs installed? Are you rendering with OpenGL? Are you using Render Multiple Frames Simultaneously multiprocessing?
The first thing you should do is update to 10.0.2 or higher... AE may be up to 10.0.3. Anyway, it's easy and it's free; go Help>Update. Make sure you turn off any antivirus or firewall software before you do it.
Second, I'm not a big fan of using Windows Media in AE. If the update doesn't help, you might consider converting that file to an lossless or uncompressed AVI. I think converting it to a Quicktime movie in the PNG codec would be even better.
Third -- and you might be surprised by this -- but 8 gigs isn't exactly a boatload of RAM in AE for multiprocessing. What happens when you turn off multiprocessing?