My mouse sometimes sticks and won't move when I'm pressing a key, rendering the game pretty much unplayable. For instance, when walking crouched I often can't look around and manoeuvre properly.

I'm running windows 7 and have tried changing screen definition but this has no effect. Can anyone offer guidance on how to eliminate this problem please?

Out of curiosity, does this happen outside the game, or in other games?

Also, is your mouse inoperable only while holding a key, or afterwards as well? And is it only certain keys, or all of them?

I've had a similar experience with multi-core rendering in Valve's Source engine games, though it happens randomly in that it either works fine or it gives a stuttery mouse constantly, it isn't something that just happens mid-game.

Anyway, yes, when I do get this problem I turn off multi-core rendering, so you could try changing the game process to a single-core affinity and see if that makes any difference (as the game was from before we all had two or more core CPUs).

If you find the problem IS related to multi-core, I don't think Kentie's updated Deus Exe launcher has an issue with them.

Thanks for your help everyone, and sorry not to have replied sooner.

I haven't been back to Deus Ex recently having been snowed under with work but I'll try your suggestions.