Computer problems: Last few days, constant browser hijacking

[Mike 03]

I have Trend Microsystems anti-virus software and also used Microsoft's live online scan last night.
My firewalls are activated, I supposedly have top-level security, but I'm getting constant new infections of programs that are redirecting links I click on from Google (not sure about whether this would apply to other links).

It's driving me nuts. It seems like my computer gets about five to twelve every couple of hours and while my Trend Microsystems program can clean them after-the-fact, it is not preventing them, and none of the updates (and I'm updating my virus protection software constantly now) seem to do anything to help this situation.

Anybody else having this? It's to the point now where it's almost useless to try to use my computer for more than ten minutes at a time without running a new Scan & Clean operation.