It probably tests Uplay's by pinging the server--or something similar--and if it gets a slow or null response decides you don't have a good enough internet connection.
KingofGnG: And here is why I won't buy a new PC game anymore (except for the upcoming DeathSpank; maybe...) until the mighty pirates'll fix it with a crack....
Good luck waiting for a crack for this; from what I've read the Assassin's Creed II crack still isn't perfect (some side quests etc. don't work), and they will have to mostly start over from scratch for other games using this DRM.
Rather than simply sending a traditional save file cut into chunks it seemingly transmits individual pairs of values back and forth continually during play. The AC2 crack database documents
thousands of these--and growing--and the vast majority will be specific to AC2 and won't help with cracking other Ubi DRM games.
This is one of the most complex DRM systems ever devised; rather than having a few carefully placed "hooks" to find and patch out, every feature of a game is tied into the server saving system and has to get the correct response back before the appropriate effect will occur in the game (like the first game, AC2 saves after every action, even just collecting a collectible item or whatnot). If Conviction only has checkpoint-based saving that might make it a bit easier, but there will still be a ton of pairs to catch.