I've just installed DD, post-patch, never played it before.
I'm running it on a E6850 / ATI4770 / 4 GB Ram rig on W7 x64. There is some mouse lag to the game, not big, but quite noticeable nevertheless.
I'm curious whether this is normal, or just a rare issue, and in case the latter is true, if anyone knows of a way to reduce it.
I've tried compatibility modes, and I am running it with UAC off.

This post covers most of the fixes for DD. Latest video drivers and . . .unchecking "Run this program in compatibility mode for:" and checking "Run as an administrator" on the shortcut Compatibility tab are some of the more useful fixes.

I'd already read through that post before posting myself, and I had exhausted all the options provided there.
Mouse input lag still there.

On the shortcut Compatibility tab, the "Run this program in compatibility mode for" is unchecked?

What sort of mouse? Have you tried single processor affinity?
High cpu or hard drive access can cause severe mouse lag for me with my logitech notebook mouse if I just use the fingernail receiver.

He appeared and disappeared . . .=)

-@Stuff: Compatibility mode is very much disabled, and I've tried enabling and disabling admin rights for it (although UAC is disabled on my system).
-@Porkdish: Currently the proud owner of a wired Benq mouse, although I've tried it with a Genius wireless. Clearly the hardware isn't the culprit here, at least not the mouse.
I've tried assigning the process to only one core, it makes no difference, the game runs fine otherwise anyway, and there isn't any excess HDD access to speak of.
Basically, the pointer lag isn't a game-killer by any standards, but it's noticeable. The delay is quite small, but enough to make it feel sluggish.
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On a more unrelated note, (I didn't want to start a new thread), what is the ztunnel flag responsible for?

I am out of suggestions . .=). . . possibly try a standard MS mouse just to eliminate the mouse you are currently using as the problem.
I am not sure what the ztunnel setting does, when I checked my setup, it was off. I have not noticed any problems. I am turning it back on just to see if I can detect a difference in game play . . .=)

Thanks for trying to help, I appreciate it.
I myself have noticed no difference with Ztunnel on or off. Also, there's a Smooth Play variable in the .div file which has zero effect on the experience, or so I've noticed on my system.

I was adding the possibility of trying a standard MS mouse just to eliminate the mouse you are currently using as the problem when you posted. My only other suggestion . . .=)
Edit: I am also using RunFirst to set affinity at the game start . . .

I've already read your post over on that thread and I started using RunFirst, but the game seems to run pretty much the same. Also, I'm hard pressed to believe that the mouse could actually be the culprit since I've already gave it a go with two different mice, a standard PS/2 wired one and a wireless one.
It's a bit strange, this lag, really, and it's quite annoying in combat, since I have to pause almost every time when picking a new target. It feels just like the slight input lag induced by V-Sync in other games.

Helpful sort, aren't you? Thanks, mate, I'll look into it now.
Btw, I thought since the patch DD runs on D3D, not opengl? Regardless, I'll post back with results.

I try . . . =) . . . good luck

I have the same issue. Like you said, it's not much, but it's enough to make the game very sluggish. I'm starting to think it's just how the game plays. If i find any solutions i'll post them though.