Ok, on the rare occasion i had this issue to, what i did was :
reinstall the mod tools, so i knew 100% they were set up correctly, making sure to add the UGX patch (not the patch for UGX mod v1.0, the patch they made for the mod tools. They are 2 different things which confuses some as the version numbers are very similar, as is the name)
then go to your cod directory in program files, select the whole thing, and right click - properties
take off read only on all files and subfolders (could take a little while, like 100,000 files)
then go into the directory, then into "bin" folder
on each exe, right click - properties and set it to run in compatibility mode for XP service pack 3 (or whatever, some people dont get that option and use on of the vista ones instead)
do all that, then open launcher and try again
Also turn of UAC controls if your using win 7 or above, those things are a nightmare, it messes with maya too