Suspicious behavior from interface, but no malicious software dete

I've been running Vista for about three months now, and lately I've noticed
some erratic behavior from the system that makes me quite suspicious about
possible keylogging or other malicious software that may have embedded itself
in my system. I'm currently running Windows Vista with Symantec Corporate
Anti-virus 10.2 Build #276 and this was the first software installed on my
computer before it ever connected to a network. I've always been very good
about protecting my system from viruses, and have only had one infection in
the last 15 years. I never open stupid emails or click attachments, I'm not
fooled by filename extension gimmicks and other stupid tricks. I don't fall
into phishing scams and I have javascript enabled per a whitelist which I use
on completely legitimate websites. All that said, it's hard to imagine that
I've fallen victim to a virus, but my system is not behaving as I would
expect it to.

It might even sound stupid, but here's the problem. If I open the start menu
or rename a file, often after only a few seconds the operation will close
itself. I click All Programs then Open Office for example, the menu will
close before I can click Writer. I click a file and press F2 to rename it, it
will quit the rename before I finish typing.

It's really quite an odd behavior, but also I've noticed my computer has
frozen completely once last week. My computer has never frozen. Lastly, I've
noticed an occasional black frame rendered. You'd probably never notice it
unless you were focused on the screen, and I don't know if this is part of
Aero or something, but it's a blink of a single black frame being rendered,
which I think could possibly be a screen capture.

Hopefully, I'm just paranoid, and there's some minor bugs in Vista being
worked out, I've ran the windows malicious software removal tool, and root
kit revealer to no results. I don't know what to do next, is there anyone
with some advice?