the log files you are finding might seem to suggest a problem related to a trojan or malicious script, for windows i quite like Norton, it does exactly what it says on the box, there are however some nice trojan cleaners and spyware detect tools, that go where norton cannot, one such tool is The Cleaner available at
www.moosoft.com then theres Lavasoft (Ad Aware) or Search and Destroy, a quick search of google should tell you where the Latter are available.
Also mIRC closing, is this a clean version of mIRC..ie:. No Scripts loaded??
ScoT
#mIRC Undernet