I found a solution for this on my Windows 7 7100 build 64bit version. Right click on mIRC.exe Click properties select "Compatibility" tab. Then check box Run this program in compatibility mode for: "Windows XP SP2" This has fixed all cpu / scrolling problems I was having before. Seems to be stable now.
-T4K
Machine specs: Intel Core 2 Quad 2.83 @ 3.4ghz, 4g Ram, ATI 4850 1Gig 2560x1600
