I will try this:
Start up your game, log in and go to whatever server & room you want to.
Then, on your keyboard, press Alt+Cntrl+Delete keys, opening up your Windows Task Manager.
Look for Crossfire.exe. It should be towards the top of the list. If you dont see it, just left click the Image Name tab to sort the processes alphabeticaly.
Right click on Crossfire.exe. From the drop box, left click on Set Affinity
This will open up the Processer Afinity box. You should see CPU 0 & CPU 1 with check marks in both boxes. Or more boxes if you have more then a dual core.
You need to have just one of these boxes check marked.
For some reason for me unchecking CPU 0 & leaving CPU 1 checked doesnt fix it.
I find unchecking CPU 1 & leaving only CPU 0 checked works the best.
Id reccomend having only CPU 0 checked, leave every other box unchecked. Bottom line, make sure only 1 box is checked.
Totti try it.