There is a problem with a particular source this morning. Signs point to it being Zodttd’s repo sending data that Cydia has a problem with. This causes Cydia to go into a crashing loop.
You should NOT need to restore your firmware to fix this problem. Please have patience, a fix is being worked on. If the coming solutions do not help there is still the possibility that a restore may be needed.
Update #1: Some good advice and instructions in the comments below. You can also try the FIXES AND SUGGESTIONS HERE, as the problem is the same as it was then. You must remove the zodttd source list that is causing the problem.
Update #2: A quick fix for some (works only if you have apt7 installed)
-Log-in as root using MobileTerminal or SSH and run this command:
-This will update your lists and then Cydia should work.