I think it's definitely the A/V part and it happens when new A/V defs are updated. I just experienced this: I had one app that was started fine, pretty fast with A/V defs 7630 I just checked for a/v updates and I got 7633 installed. I started the same app right away and it was dog slow, I think it needs to be validated against the new virus defs. Now if I restart the same app again, it's fast, I suspect until the next a/v defs. What doesn't make sense is that having the A/V set to On Access or Stateful does not make a difference. On Access I'd suspect it should always be slow as the app is scanned every time.
It's disappointing to see that the A/V has issues again, historically the A/V caused troubles in CIS and many times I had to disable it and use some other A/V software.
I'll disable the A/V completely and see what happens.