I too have installed Android 2.33 (Gingerbread) so only have the option of the "AT&T software update" - the HTC wi-fi software update option is no longer listed. When I attempt to check for updates using the AT&T option, however, it results in the error: "Server Unavailable".
I've seen this cited in other posts, and users typically used the HTC wi-fi update to bypass the issue, but since the HTC option is no longer listed, how can I check for updates from my phone (other than going to the HTC website to check for manual downloads)?