there are serveral notes about this around a few forums and evan a few explaing why as i had to do a search myself as i had a simerler problem .
however you can get around this by temporaraly disabling antivirus if your only playing the game this shouldnt be to much of a problem .
now im not saying that any1 should leave themselfs unprotetced but if your not curently downloading anything while playing this game
from any of the numorous download sites those ligit and those not it shouldnt cause a problem .
it is also worth noteing that the virus protection on windows 7 is actualy preaty good however i have not had it running since i use a 3rd party out of habbit so have no idea if this will cause problems with FL/CF
if your running wiondows 7 disable your current virus checker and try the inbuilt programe you never know.
failing that some virus checkers alow you to add exceptions so you may be able to tell your virus checker that those in FL actuly are ok and not to panic
i hope this helps a little
p.s
its also worth noteing that if your running vista or higher to run CF as administrator otehrwise youll have more exception errors after instaling with the virus disabled
if you take this link and scroll down theres a whole chunk of user request regarding this and other loadup isues and some answers by the admin team
http://www.moddb.com/mods/crossfire/downloads/crossfire-181