This, along with the no music glitch after you beat the game are 2 of my biggest problems with ACR singleplayer, I doubt this game is going to get any more patches though, because as Serrachio said they're busy with AC3 and all their attention is focused on that.
Originally Posted by Terrence_Lee
After that, ubisoft had several update uploaded, but none of them fix the bomb challenge glitch, all they put into the update is to make the multiplayer better.
They didn't make the multiplayer better, they made it worse.
I got around this glitch on pc. I uninstalled and reinstalled the game (keeping my save file). The next time I launched the game I closed the autopatcher and started playing. Afterwards I just worked towards the requirements for the challenge.