I found avast fairly useful for a couple of months, including identification of two Windows trojans in my Mac e-mail archive. The user interface takes some getting used to. But all in all, I considered avast 2.74 worth licensing for one year.

But that's changed now that I upgraded to OS X 10.6.1.

Now I cannot quit or even Force-Quit avast. Attempting to present the issue to the avast forum, I find at least one other user -- in the Netherlands -- is equally frustrated by persistent avast despite all ordinary efforts to shut it down, quit and force-quit.

Until their software team figures out that some of us are troubled by quirks not seen until OS X 10.6.x and unable to troubleshoot by isolating avast, beware of installing it.

And if installed, check their forum before upgrading to OS X 10.6.