It might be a bad (or missing) installation of the .NET Framework 2.0/2.5. If I recalled the viet hack requires version 2.0.
The other is that it's probably an antivirus like Symantec. I've seen this problem before and it's usually the antivirus at fault.
See

for information about the same issue with another software app. It's the second post from the bottom by Will Buffington.