You're probably using some script or DLL that is causing the slowdown.
What is the result of typing the following in mIRC:
//echo -a $md5($mircexe,2) $script(0) $dll(0) $com(0)
On a sidenote, what is it about the new version that you "can't stand"? Is it the many bug fixes? All the new features? Better scripting support?
Result of echo:
d20dd1be97ee43da4e7efd0030af834f 1 0 0
Really, I don't like the new buttons in 2.0. I'm used to the older version skin.