If this helps, I can confirm that McAfee products, including SiteAdvisor, can co-exist quite happily on the same PC. I have SiteAdvisor Version 3.2 (Build 3.2.0.152) which of course runs all the time; I also have, installed but not running unless I want to do a scan, both Spybot and Malwarebytes. When the major upgrade to McAfee 2010 took place it went through without any errors or warnings; so the problems probably occur if McAfee detects that some other software (Spybot, in this case) is currently active. And I would most definitely not have TeaTimer running at the same time as McAfee; I tried it for a few days and then disabled TeaTimer because it and McAfee were fighting all the time.
On my setup I can run Spybot or Malwarebytes scans when McAfee is active without any problems at all.
I hope that helps a little.