Third-party Applications broken Some third-party applications will no longer function properly under iPhone OS 2.2 due to API changes and other modifications. These include a number of applications that make use of CoreAudio. These applications will generally need to be updated by their developers. However, you can try uninstalling then reinstalling applications for problems that do not involve API or other strict compatibility problems.

“Could not Connect to Internet” Some users are encountering an inability to connect to the Internet over cellular networks after the iPhone OS 2.2 update. In some cases, this issue can be resolved by switching from 3G to EDGE (or, for carriers other than AT&T, the appropriate GPRS network).

“SIM card not inserted” or PIN lock Some users are receiving an error message indicating that the SIM card is not inserted, or that a PIN lock is in place when none should exist.

Problems deleting email Some users are unable to delete emails from certain accounts, especially AOL accounts after the 2.2 update. This problem can generally be resolved by navigating Settings > Mail, Contacts, Calendars > (Your account name) > Advanced > Deleted Mailbox, then setting for the “On My iPhone” Trash for a POP account, or “On the Server” for an IMAP account.