Please list here all known security softwares which DT has problems with, so i can try to check what feature of the security softwares is interfering.
F-Secure (fixed by latest F-Secure updates)
ZoneAlarm (Free and paid)
Solutions for these are posted in our help document.
Please only list problematic non-listed security softwares, thank you in advance.
ThreatFire is sadly completely incompatible, you would need to kill its service completely (no option to disable available there) and that is rendering the software useless, when the service is disabled.
Comodo Internet Security 2011's Defense+ is interfering with DT. Therefore you have to deactivate the service completely and reboot (Defense+ tab -> Defense+ Settings -> Check "Deactivate the Defense+ permanently (Requires a system restart) -> Reboot)