The point of allowing you to switch to the old version is in case
there are any compatibility problems you might run into. The new
version has more features and has received a lot of speed
optimizations.
Ryan
As for your antivirus software, if the Gmail Help says it will cause
that error, then that's the problem. There are other AV options which
don't have the problem, assuming you don't need some particular
feature that PC Tools offers. I personally love Avast, which has a
free (other than completely spam free registration). The home version
can be found at http://www.avast.com/eng/download-avast-home.html
Ryan