Force Triple Buffering on for Titan Quest.
Go to the \My Documents\My Games\Titan Quest\Settings\
Open: options.txt
Find: TripleBuffer
Change to: TripleBuffer=true
(default is false (or off)
If TripleBuffer does not exist, add it
You can also force TripleBufer on for the game in the nVidia Control Panel Profiles section, create/edit the profile for Titan Quest and enable Triple Bufering for it. (But still edit the options.txt file as mentioned above)