This problem happened for a few moments yesterday, because we had a missing file on the Live Update server, but it's now fixed. If you still have it now, even after running the Live Update, then the error message is right, and the problem is your antivirus.
Of course, the antivirus is only the most common problem. There might be other causes for this, less common, such as missing VC++ libraries. The "Missing/Corrupted VC++ libraries in your system. See solution in the "Addon Manager not showing up in P3Dv4 **SOLVED**" thread should give some suggestions how to fix this:
http://www.fsdreamteam.com/forum/index.php/topic,17484.msg122656.html#msg122656The full GSX installer DOES install the VC++ libraries but, in some cases, you might have to RESTART WINDOWS after installing GSX, in order for the VC++ libraries installation to be complete.