A lot of people who recently jailbroke their iPhones are having issues with Cydia crashing when launching it. There is a quick and dirty fix for that and it requires to either SSH into your iPhone or use iPhoneBrowser and delete a few files.
Apparently the problem is caused by some corrupted repositories that make Cydia crash within the first few seconds of loading it.
To fix this, simply navigate to /var/lib/apt/lists and delete all the files in this folder except for the folder called “partial”.
Then reboot your iPhone and launch Cydia. It should load without crashing.