1. are you useing the newest version of mirc ? ( 6.03 )
2. what os are you useing? windows .. 95 ? 98? 2k ? me ? xp ? etc.
3. try to find a way to reproduce it, a unique thing that always happens right before it happens ? when u click on something? when you do something? .. when does it usualy happen that we might try to reproduce it.