Why doesn't Norton permanently block scr.malcode!gen?

About 10 minutes after I start my laptop, I get a Status Update message from Norton that says" Auto-protect is processing security risk Scr.malcode!gen. After about 20 minutes, I get a message from Norton that the threat is resolved and no further action is required. I clicked on the File Insight option, Activities, and it says “File:mshta.exe (Scr.Malcode!gen) - No fix attempted.” I was on the computer for more than 2 hours with a Norton employee, who tried to fix the problem, but it is not resolved. If Norton knows that this is a high risk threat, why aren’t they doing something about it? It slows down my computer terribly. Anyone know what’s going on here?