It seems best practice to have only one active firewall, anti-virus, and anti-spyware application running on the system at any time. More can actually result in less protection, and create system conflicts/problems.
So~ best to choose one of these: AVG anti-spy, Ad-aware Ad-watch, Spybot Teatimer, SuperAntiSpyware client. Personally, I would go with AVG as the full-time, and reduce the others to scan-on-demand, and run them each once a week.
Any number of "scan only" programs can be used one at a time.
My personal experience is that SpywareBlaster and SpywareGuard "play well with others."
SpywareBlaster, of course, does not run full-time, and SpywareGuard seems to create no conflicts with my AVG anti-virus, Comodo firewall, and A-Squared AntiMalware full-time client.
One rarely hears about WinPatrol causing any problems whatsoever. It is actually a different sort of application.
If you are experiencing trouble after selecting one anti-spyware client, I would suspect Norton. There really are better alternatives. It gave me so much trouble that I tossed it out with 9 months left to go.
For more of what I have learned about layering my security, see my Vox: http://doc1101.vox.com/
No ads, no cookies, no live links, just info.