Malware detected in PC but not on a Virus Total

Often I submit files that where detected in my PC to a Virus Total.
In results of Virus Total under Comodo there is no threat detected, but CIS on my PC detected it.

  1. CPU Athlon 64 X2 4600+
  2. Windows XP pro, service pack 3, 32 bit
  3. CIS 3.8.64263.468
  4. Antivirus - default settings
  5. Firewall - custom policy mode
  6. Defense+ - clean PC mode
  7. Administrator account

This thread tells you how to report false positives.

I reported it.
Just strange that CIS 3,8 in my PC detects a malware, but Comodo on Virus Total does not.

Malware was detected by heuristics or by database? Maybe on Virustotal scanner doesn’t use heuristics to avoid false positives? I’ve had lately some FP but all were caused by heuristics set to medium/high. I sent these fp to malwaresubmit few days ago but with actual database those files are still detected as heur.pck.unknown.