iPhone Update Re-Configures Gmail Accounts

According to this Google FAQ, installing the iPhone 1.1.3 update will automatically update your gmail settings from POP to IMAP:
If you configured Gmail access on your iPhone by tapping the large 'Gmail' icon in mail setup, please note that installing software update 1.1.3 will automatically convert Gmail on your iPhone from POP access to IMAP access. This means that actions you take on your iPhone will now sync with actions in your Gmail web interface (i.e. messages you read on your iPhone will show up as 'Read' in the web interface). This also means that messages you delete on your iPhone will be moved to the Trash folder in the Gmail web interface, and thus deleted after 30 days. Please exercise caution when deleting messages, as this behavior is markedly different from POP access.

Fuente: MacSlash