Hmm, strange behavior on the task manager part, wanting to restart.
I know that some trojans and virus like to hide the mirc under different names,
i cant remember which version Khaled introduced the no renaming of mIRC exe files
some trojans use earlier versions of mIRC to do their work, but most Antivirus
programs out there should detect them and remove them.
On a side not what Operating System are you on ?
If it is windows xp, you could Click Here
and follow Parabrats suggestion, not sure if i can help you anymore than i can