Sometimes, my computer inputs are not registered by the game for durations upward of 5 seconds. This includes both pressing buttons and letting go of them - I can tap a direction key for a split second and end up walking through an entire line of spikes before I regain control. It's not an FPS drop kind of lag (I do get those often as well, but that's a different problem for another time), as the actual animations are smooth enough to be playable. I can see fellow party members move about and attack, but I'll be running into every single wall and trap in the area. The best I can hope for in these kinds of situations is to hold down my shield button and hope it comes up before I'm mincemeat.
I'm fairly certain it's input lag, as it also pops up when I'm trying to type a message. My sentences often get distorted a little liiiiiiikkikikiikikieeee eeee tttttttthhhhihiiishss.
There doesn't seem to be any particular situation where it arises, but I'll note that the only times that I've actually noticed it happening were when I was in a party with other players. It may be coincidental, and possibly because I'm more able to complain about it in a party, but I'll just throw it out there.
Any troubleshooting ideas?
Computer specs:
Windows Vista (64-bit)
Java 1.6.0
1.60 Ghz processor (AMD Athon Neo Processor MV-40)
ATI Mobility Radeon HD 3410
1278 MB graphics memory
2 GB RAM
EDIT: Also, playing through Steam.
My first guess is something with drivers and the hardware polling rate, since the rest of the process doesn't seem to be impacted. Do you have any other games that can be played on it in full screen mode to see if the behavior extends to other apps?