CIS 6 Antivirus issue with firefox

I’m not sure if this is a bug or normal behavior, on Firefox, i tried to download,, &, comodo does not flag these file as malicious file and allowed it to be save to the c drive, but when i tried to save to another drive, comodo immediately flagged it as malicious file before the download starts.
On the other hand, when using IE10 to download these files, be it saving to c drive or another drive, comodo will flagged these files as malicious b4 the download starts.

This happend to all my computers at home, 1 desktop & 3 laptops all exhibited the same behavior.

I’m using Windows 7 64bit amd Comodo Internet Security 6.0.264710.2708 with latest virus definition
Firefox version 19.0.2