iPhone OS 2.2 Re-Locking Some Legally Unlocked Phones?

While the issue is not universal, some users are reporting a problem in which the iPhone OS 2.2 update locks legally unlocked iPhones (sold in Hong Kong, certain countries in Europe and elsewhere). The issue may occur if a legally unlocked phone is bought in one country then updated to OS 2.2 in another country. Among the user reports from this Apple Discussions thread:

“Bought legally unlocked iPhone in Hong Kong. Updated to 2.2 in Germany. No my iPhone seems to be locked.”
“I bought my iPhone 3G legally unlocked from HK, and I just upgraded to iPhone 2.2, but it seems my phone is locked now. On the phone it says emergency calls only and iTunes is saying not supported SIM.”
Many other users are having no problems with legally unlocked phones after the update.