Used SecuROM 7.x copy protection. The single-player campaign will not run if of Process Explorer older than v11 has not yet been run for the current boot. Or if Process Explorer v11 or earlier has been run in the current boot. Or if some versions of FileMon and RegMon have been run in the current boot. The exact details of the cause of these problems have never been fully determined.
About World in Conflict
For some reason I didn't experience this problem, nor have I heard of it anywhere else.
After looking on the web, it seems the exact nature of the problem is not fully understood. Since this is copy protection software, the companies involved have little incentive to publish the details of how it works, so this problem may never be fully understood.