Ah - I was running Spywareblaster too so maybe that was part of my problem? Anyway - I followed some of Gizmo Richard's recommendations/reviews and am currently using the personal editions of Avira AntiVir, Sunbelt Personal Firewall and Spyware Terminator along with Sandboxie for potentially unsafe browsing or other operations. I find this combination a lot less heavy on resources than my previous setups. However I constantly keep this sort of stuff under review depending on the latest updates/feedback on such tools.
I'm using Spyware Blaster with AVG, Spybot, ZA etc. Not noticed any problems. Never notice the scanning speed as don't use the schedule scan, only manual scan and usually only kick it off before going off to do something else. Maybe it loads a bit slowly on startup, that would be my only complaint. I tried Kaspersky Internet Security on Vista but it nagged me too much. So I'm back on AVG.
This software is now considered malware as it does not act as it should do for a legitimate program. That is, it is now classed as rogue software, wasting your bandwidth, data quota, and putting undue load on other websites.