Spybot Beta User Problems

hi developers,

System info:
OS= WindowsXP pro SP3;
State of the System: very dirty;
antivirus= Antivir;
Browsers= firefox, explorer, chrome;

multiple processes running: winamp, firefox, IExplorer, explorer,

Operations:
Installed the new spybot at noob. worked fine
Started immunisation. worked fine

Direct after starting immunisation i started a full system scan.
At that moment 2 scans started, and i got a bad system responce.

Protection for starting A scan process thats already active would be nice.
hope u find my experiance usefull.

Greetz TjaardA