I have Jailbroken my touch and everything worked without crashing until I installed Summerboard. After that, it would randomly crash while playing music, watching video, whatever. So I went to uninstall Summerboard. My dock got locked up at the top.
As a result, I restored the iPod, re-jailbroke it (all on a Windows machine mind you) and re-installed all of the other applications, minus Summerboard. Everything runs just fine, no crashes.
I hope this helps narrow down what is plaguing you. My personal thought is that it is the alpha version of Summerboard.
Agreed. I'm putting my money on Summerboard. I uninstalled it and everything works great so far. No crashes or anything for anything. Theme might be gone but thats a small price to pay for it being stable.