CIS 3.9.xxxx.509 hangs on manual scan

I m using CIS 3.9.xxxx.509 x32 bit
Windows xp sp3
no other security application other than CIS installed on pc.

When i click on manual scan, Antivirus starts scanning winlogon.exe file and keeps scanning it only.
I cannot stop scan or even close scan window when this happens.
But this problem dont happen all times when i try to scan manually.
can someone tell me why does this happen at times & how can i prevent this from happening. ???

Is this a clean or upgrade install? Does the same thing happen with a clean install in case you had an upgrade install?

This is upgraded install from 3.9.xxxx.507 to 509
Manual antivirus scan dont hang everytime, after writting problem in this thread i done manual scan and it worked it did not hanged at all it completed scan properly.
Now the question is why it hanged before at winlogon.exe?

That link indeed helpful, and yes i have my heruisitic on HIGH also, A clean install will solve the problem so i will go and do it now:) Thanks alot Eric & Tarantela for help. (:AGL)

Ok i did fresh install of CIS 3.9.xxxx.509, Then i let the value in manual scan setting be default (low heruistic) & did scan, the scanning completed without any problems,
Mod. if you want you can close this thread now.