Most motion graphics designers, animators and visual effects artists, who use After Effects regularly, must have sometime encountered horrific nightmares with their software. Adobe After Effects is as fragile as a brittle glass. Once it crashes, it is not going to get back on its track.
Parsing properties list is an error usual occurs when the software was not quit properly. Solution is pretty simple. All you have to do is delete the after effects application data files.
On Windows Vista
C:\Users\* Username* \AppData\Roaming\Adobe\After Effects\9.0
Change * Username* with your account username. The version number 9.0 can change according to your software version.
On Windows XP
C:\Documents and Settings\...
Delete all the files and folders in this folder or you could just move them to some temporary location for backup. After deleting run After Effects and it should start. It will re-create all the files and it will be like the day you installed the after effects, with all default settings.
There's more information here:
http://blogs.adobe.com/toddkopriva/2009/02/crash-on-start-with-error-pars.html
You should update to After Effects CS4 (9.0.2), which fixed several crashing bugs, including this one:
http://blogs.adobe.com/toddkopriva/2009/05/after-effects-902-update-red-r.html