I followed the steps you described but have not been able to reproduce it yet. I tried various combinations of display settings, moving the switchbar to the top/left/bottom/right, and so on, but the issue has been pretty elusive so far.
If you copy the v6.35 mirc.exe into an empty folder and an empty mirc.ini file to the same folder, and then run that mIRC, are you able to reproduce it with the default settings?
