I have an iphone 3G originally on ios 3.0, unlocked and jailbroken. Cydia was crashing after I added a bitesms beta source and I couldn't fix it. Ultimately, I restored and rejailbroke (multiple times) to ios 3.1.2 using redsnow and blackra1n, but cydia crashes during the reloading page (after it downloads the packages).
Prior to restoring and rejailbreaking my phone, I did
"su
alpine
apt-get remove cydia
Yes, do as I say!
apt-get install cydia"
in terminal, but it didn't work. so i decided to just restore my iphone.
I have also tried usb connection to view iphone directories and deleted files (acc to How to Fix Cydia Crashes)