Windows restart failure

Here is one to toss into the pot.

About a week ago my restart time, prior to a boot into my other OS, began to slow, I mean really slow.
Eventually it stopped altogether. I must say, here, that shurdown was not affected.
I remenbered reading something on the web about this . Most of the suggestions led to one cause - Avast. I disabled Avast, a couple of boot ups - no change.
I checked for unneeded services - nix
Msconfig startup - no
Virus or spyware - no
The logs did not show anything suspicious.
I wanted to file a bug report, but also wanted to file a possible reason but was unable to under the circumstances.
No big deal. I reinstalled 7 and everything is back to normal. I was still apprehensive of Avast so I have changed temporarily to Avira

Any thoughts? Anyone else had the problem?

As you can see, in my post, I found no problems with Avast. Anyone got anything in some other direction? I am not expecting it to return - just curious.