error 3.3.0 Upgrade Check Failed !

[hameau]

... so I still suspect timeouts or our host is blocking known spammer hosts, it has been doing this since we switched to mt many months ago.

Host (Media Temple) level blocking is the most likely, imo. The version check used to work for me, but I don't know when it stopped. I get a timeout with or without curl and with a limit of 10 seconds (beyond that, it's no use anyway).

The IP address of my hosting server is 213.186.33.2: you might want to ask Media Temple if they are blocking that IP and, if so, why. It doesn't appear on any of the recognised blacklists (e.g., http://whatismyipaddress.com/blacklist-check).