The newer version of CKeditor included in mojoPortal 2.3.6.4 has updates for IE 9.
However, if you're getting errors about long running scripts, it could be caused by any custom javascript or jquery plugins you are using. If you are using such, you might try eliminating that from the equation and see if the problem persists. I have not noticed any IE crashing at all using the skins included with mojoPortal and unless others also report it it seems more likely caused by something custom with javascript.
I notice also that your skin has a meta tag added by Artisteer that tells all versions of IE to emulate IE 7. You may want to make that only apply to IE 8 and see if it helps. I notice that newer designs from Artisteer 3 make it emulate IE 8, so it seems like Artisteer may be a version behind in support for IE. Possibly the javscript added for Artisteer has some problem in IE 9.
I would also try it from more than one machine and verify it is not a machine specific problem with the crashing.
Hope it helps,
Joe