Ok, Summerboard IS buggy... I swear to you and if you have trip1pogo installed at the same time, its EVEN more buggy.
The optimal solution would be to be able to change the background image without using summerboard. Also, do a manual jailbreak so that you understand what you are talking about.
If you have your applications folder symlinked, it will cause crashes as well esp. if you have native ipod apps in the same folder as your 3rd party apps.
also, summerboard has a power management issue that will randomly kick wifi dependent apps.
Ive heard tons of people say summerboard works fine to come back the next day to say that it crashes everything...
Good luck!