I'm also affected by what I think is the same bug: Since upgrading to mIRC 7.42, the "order history" of clicking channels open and then pressing escape again to go backwards in the order history is broken. This has severely impacted my workflow in mIRC as I regularly switch back and forth between channels, and now this is not possible anymore. When I now press escape it minimizes the current channel window and that grey background appears as if all windows are minimized, I always have to click the channels manually to open them again.
This issue also seems to only appear when doing this with maximized windows, non-maximized windows do not seem to suffer from this bug.
