If Vendetta Online starts without focus, the whole window system is stuck. IE: If I click on a Firefox window right after starting Vendetta, right before it takes over the screen. Vendetta will start without focus, and will somehow be unable to get it. However, no other window will get focus either. So I can see the Start Menu if I press the Windows key, but it vanishes instantly. Likewise, I can open Task manager with ctrl-alt-delete, but it vanishes instantly. However, no amount of pressing escape will cause Vendetta to quit, and the mouse will not respond to clicks. This is a bad bug, since it requires a hard restart of the machine to fix. I can't even double-CAD for some reason. Not sure why.

Windows XP w/SP2

VO loses focus for me too if I have something else open, though the trick for me has been just to cursor to the upper left and retireve the VO cursor. Same OS as you, but no Firefox

It happens to me with any app, not just firefox. And moving the cursor to the left didn't fix it.

This happened to me at home a couple days ago. I only had VO and an explorer window open to the Program Files/Vendetta folder where I ran VO from. This was on XP with sp1, Not sp2.

Basically VO seemed to not grab focus and the cursor was the Windows cursor. Whenever I clicked, the explorer window tried showing itself (I must've been clicking on it) and then immediately went away, showing VO again. I kept clicking around until I must have clicked on the VO window and then VO gained focus. Very strange indeed since fullscreen DirectX shouldn't allow this at all ever.

This was WinXP/SP1 with a radeon 8500.
I've never had the problem at work with Win2K and any card. Of course I always run VO in window mode because it's easier to debug.