NIS 2012 Suddenly detecting hundreds of risks for safe files.

This morning NSI 2012 gave me a "Threats Detected" window that lists hundreds of files that I have had for years and is saying they are a "High" risk.

 

Sample below

 

Unresolved Threats: Risks in compressed file "Skype.msi"  Type: Compressed  Risk: High (High Stealth, High Removal, High Performance, High Privacy)   Categories: Heuristic Virus  Status: Not Attempted  -----------  1 File [skype.exe] inside of [______] inside of [c:\programdata\skype\{d6f879cc-59d6-4d4b-ae9b-d761e48d25ed}\skype.msi] - Not Attempted

 

So far as I can see these are ALL safe files that I have had on my computer, in some cases for years.

 

What should I do?