The first issue appears to be a Windows Vista bug. I reproduced it some months ago in both mIRC and other MDI applications. As far as I know there is no way for mIRC to resolve this issue itself.
The second issue I have been unable to reproduce so far. Are you using a single line editbox or a multi-line editbox? Does it happen only in certain windows, eg. channel windows, or in all mIRC windows?
