Cydia Problems
As of 2:30 P.M. Central time cydia wouldn’t open for me. I have been reading all around the net and it seems as if this problem is affecting a lot of people. I believe that the problem is with a package called 3g unrestrictor which was released in the cydia store early this morning. Somehow that is affecting cydia’s server side and is not letting Cydia run or open. I advise all to just be patient and do not keep trying to open cydia, Saurik is working on this problem and will have it up in no time.
It seems the problem with cydia crashing is that some of the source files have been corrupted. I personally only deleted the bigboss.apt lists as said below and my cydia is working just fine
Update: Oranav just tweeted a fix for cydia crashing issues. His tweet states, delete everything that starts with apt.bigboss in /private/var/lib/apt/lists/ thanks to CrashX

July 18th, 2009 at 9:40 pm
I can not even open Cydia – How do you expect me to delete files
July 18th, 2009 at 9:46 pm
you don't open cydia you ssh into your iphone and delete go to private/var/lib/apt/lists/ and delete the 3 files that have the word bigboss in it and it will fix the cydia crashing issue
July 19th, 2009 at 4:57 am
Hmmm. after deleting apt.bigboss files in /private/var/lib/apt/lists/ (cydia still crashes) and then re-jailbreaking with redsn0w only ever installing cydia and not icy, cydia is still crashing on launch. And I had no problems with cydia before today. Thanks for any suggestions
July 19th, 2009 at 12:41 am
I guess one solution that worked for me is to re-jailbreak using redsn0w if your device is already jailbroken on 3.0, however this time don't tick the box that says "Install Icy", just have the Cydia box ticked. After this everything worked perfectly and the best part about this is that you do not need to restore.
July 19th, 2009 at 12:40 pm
This worked for me! I ran this command in mobile Terminal: apt-get install cydia (after entering "su" then "alpine") It told me that it could no longer access files from sinfuliphone.com repo in /private/var/lib/apt/lists/ . I deleted those files and cydia is working again. So if any other files are corrupted and causing problems that will tell you which ones to delete.
July 19th, 2009 at 8:27 pm
Still getting "Unable to load (timed out)"
July 28th, 2009 at 7:47 pm
I follow the instructions but still not working…
Plz help~