Some original games do not work when a certain application has been installed, like DAEMON Tools.When using Fixed Files make sure to use a Firewall which controls outgoing traffic, as some games call back to report the use of these modified files!.When this happens use the original EXE to play online, else you could find yourself banned from the game! Some No-CD/Fixed EXE files work fine in Single Player mode but are detected to be modified when trying to play online.
Disabling desktop composition in compatibility options or running the game in compatibility mode for Windows XP Service Pack 3 appears to fix the issue.
Some users report that after alt-tabbing from the game in Windows 7/8, refocusing the window and then clicking the mouse will defocus the window again, making the game unplayable after alt-tabbing. If you are running Raptr, try closing it before opening the game again. It can be caused by Alt+Tab'ing/minimizing the game, although some users have reported the use of the program Raptr as the cause. This issue revolves around the inability to use the mouse in the in-game menus as the pointer will not appear, and has been reported by several users. Sometimes the zoom controls will cause the scope zoom to zoom in and out continuously. Reportedly the game crashes after a kill in some instances. The developers are aware of this issue and the next patch will reportedly fix some of the problems, most notably the fact that connecting to a dedicated server means you are subsequently unable to connect to a P2P server. Some users have reported an inability to connect to some or all multiplayer servers.