My iPhone's IMEI

This morning, my iPhone's IMEI was perfectly fine. My iPhone has never been unlocked. I was able to use my AT&T Pick Your Plan SIM. And as recently as a week or so ago, I wrote about using iASign, which picked up on and used my normal, correct IMEI settings.

Today, as I liveblogged, I finally applied the 1.1.1 upgrade. This afternoon, when I finally got around to trying to reactivate my phone, which was displaying the "wrong SIM" message, I found that the iPhone update had apparently changed my IMEI to the dreaded 004999010640000. I cannot figure out any other way that the IMEI had changed. When I last used iASign, it showed the correct IMEI. Today, not.

Basic facts:

• My iPhone has never been unlocked.

• When I used iASign the last time, my IMEI was correct and I was able to switch between my two AT&T SIM cards.

• I did pitch in very peripherally with the unlock effort. However, I used a version of the program that had every baseband access commented out to keep my iPhone pristine.

• I have two AT&T accounts: one is an iPhone-specific PickYourPlan. The other is a general PayAsYouGo. I have switched between these two SIMs on a regular basis.

• iASign will not work and will not let me switch SIMs unless it detects a proper IMEI. It no longer does so.

Update: On Dinopio's advice, I removed my SIM--and the iPhone reports the proper IMEI. He suspects there is something corrupt on my baseband.