Is there a way to roll back Avast to the previous version?

Avast has worked just fine for me (and this computer) for the last two years. These problems only came up with the most recent update.

I’ve done the defrag thing. I’ve also done a virus scan. I’ll scan for spyware too, tonight. I’ll have time in a couple of weeks to do a thorough cleaning of the system, there’s plenty of clutter on here. There should be enough hard drive space, but it wouldn’t hurt to have more.

I do appreciate people’s help, don’t want to give the wrong idea. What’s weird is sometimes the system works fine – other times, the Avast icon starts spinning round and round and everything slows down.