Different SIM, now everything force closes

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I've got a UK Galaxy S on T-Mobile, it's not branded in anyway and I was under the impression it was unlocked. I just tried an Orange SIM in it, but it didn't work. I put my T-Mobile SIM back in, and now I get greeted by everything force closing when I turn the phone on.
I can't get into Clockwork Recovery either, I can get into the stock recovery, but when I try to flash the update.zip it just says replacing recovery with clockwork recovery and then hangs.

Any ideas?

Edit

Well, I wiped data and restored from Titanium backup and now everything seems fine. It seems my clockwork problems are because I installed the voodoo lag fix yesterday, so at least that's a known issue.
Can anyone tell me why putting a different sim in my phone would have broken most of my apps?