Hi,
Be sure that my KAV is up to date, I update it every evening, and I'm absolutely sure that I'm not infected by any kind of virus nor trojan.
Keep in mind that it isn't when scanning the mIRC.exe executable that I got the alert, but only when the process mIRC is launched.
My mIRC is free from any kind of scripts.

For info I run it on a XP SP1 system,
my version of mIRC is 6.0.3.0 (unregistered),
my version of KAV Scanner is 4.0.5.37,
KAV Monitor is 4.0.6.0,
KAV Mail Checker is 4.0.5.1,
KAV Office Guard is 4.0.5.0,
KAV Anti-Script Checker is 4.0.5.0,
KAV Updater is 4.0.5.0,
KAV Inspector is 4.0.5.0,
KAV Control Centre is 4.0.5.13,
and KAV Core Components is 4.0.5.31.

Don't be rude about my bad english, and
thanks to all for your help laugh