COD 4 - odd popup

[#1]

I keep getting this popup when COD 4 single player starts - any idea what is causing it and could it fall foul of the DRM system

[#2]

Should have googled before posting - it is a common problem and may be due to running Vista

[#3]

if you havent already run game as admnistrator  that might help

[#4]

I get the same regularly on XP, it happens on COD:WaW too. I've never actually looked into it so not sure what's causing the problem.