In reference to some of the things in https://forums.mirc.com/ubbthreads.php?ubb=showflat&Number=208299&page=0#Post208299

I have been experiencing on multiple machines(all running vista/2k8 x64) extreme slow downs that show up in the perfmon results as a full cpu usage in the main thread.(Usually with many channels loaded)

The issue lasts for a few seconds and reccurs fairly often.(the whole ui becomes unresponsive)

It is unrelated to any loaded script as far as I could see(disabled them and the issue still occured).

Studying stacks during the freeze shows them always occuring in the main place in the main stack:
[... uninteresting top of stack since it's consequence of a win32 call...]
USER32.dll!LoadImageA+0x29
mirc.exe+0x23906
mirc.exe+0x15db1a

(originating addresses in mirc.exe do not change).

I am unable to find out what those functions are in mirc since there is(understandingly) no debugging info.