Got an interesting conundrum here and would welcome any suggestions...
Have played through AC2 almost to end without major problems, however - am now entering (I think) final level in Rome. I start the initial climb up the tower wall above the river, and get near the top where there is a single protruding stone to grab before reaching the castellated parapet wall. Ezio jumps up but WILL NOT grab this rock! I have watched walkthroughs on Youtube etc where he simply grabs the rock and continues climbing, but in my case he fails to connect and falls back every time to the previous handhold.
Have mailed Ubisoft support but got no joy as yet, would welcome any thoughts or suggestions that don't involve clearing cache and starting again!