Do you have more than one firewall running? If so, disable one and see if things improve.
Do you have an anti-virus program running? If so, disable it temporarily and see what happens. If that solves the problem, poke around in the AV program's settings/options/preferences (whatever they call it) to see if there's a way to tweak it.
Finally, if you haven't already, download, install,
immediately update and then run
Spybot and/or
Ad-Aware. Read the help files to familiarize yourself with how they work. I recommend you use them both since each tends to find things the other misses. Let them clean up any spyware found.
Then, to be doubly sure, download and run
CWShredder.