I've seen sites that changed and aren't exactly the same as they were years ago. And I've seen sites that were hacked and contained malware.
And I've seen false positives.
In your case, I'd contact the webmaster of those sites.
Malicious URL Blocked
avast! Network Shield has blocked a harmful site.
Windows 7 on PC
Help! Why are sites I've used for years getting this notice today? What do I do? (It's happened to 3 out of 4 times. Help!