To make sure you have all the files needed, restart your PC. It's very likely to be true though, but as I repeat many times, we will discover that when it's already too late, that's why I'm bullet-proofing and not waiting for an armageddon. If its not caused by anti-virus software, the issue could be a corrupted file or failed download. That is only a pure theory though based on my knowledge and experience with Steam internals I've been analyzing while creating ArchiBoT and ASF. Assuming that is true (because once again, I don't have VAC documentation), if IM dll will be ever considered by VAC as malicious, either intentionally or accidentally, people can get VAC banned by running IM alone and not even playing anything at the same time.

I suspect they're being used as supplement to normal VAC game scans, but ArchiBoT received one offline request without even having any game launched, therefore I'm sure that the logic is not only connected with game scans, but offline periodic ones too.

They're not documented, like entire VAC, but Steam network might ask Steam client to perform such scan on-demand, and in fixed intervals. Scans made by Steam client discovering hooked DLLs to Steam client or SteamService.exe (background service you can find e.g.