Yeah, repair permissions or try shaking a rubber chicken on top the machine - it'll help about as much
If you're getting permission related error messages on your operating system files it might help, otherwise it's
a waste of time.
Repairing permissions is a legacy from the time people ran non-OSX software os OSX. Because old OS 9 software
had no knowledge of permissions they tended to screw them up. And it certainly won't free up any memory,
if you wan't to know why you might be seeing more free memory after repairing permissions you might want to read up
on virtual memory, paging and caching on modern OS's/filesystems...
If you want to know why a program crashed, look at the crash report that gets written in your
home directory -> Library/Logs/CrashReporter. The crash report will tell you what the software
was doing at the time of the crash.