mIRC beta v7.65.676 ‒ It seems I found a way to reproducing this bug. In any case, I manage to repeat this many times.

     1.Start the mIRC client as usual. Customize so he performed joins to multiple channels at once (standard methods).
     2.Connect to the network and leave one of the channels open. The client does not have to be minimized.
     3.Start the program "Photoshop". I have "Photoshop CS6 x64".
     4.Now go back to the open mIRC client window. ‒ You can already see that the list of nicknames "Listbox" has gone beyond the "Toolbar".
     5.Now click 2 times on any of the nicknames in the list to open the private window. Ready done! All bugs are now visible.

In addition to the previous screenshots left by the posts above, I am attaching a new screenshot, where you can see the shift of the list of nicknames outside the "Toolbar":

     [Linked Image from i.ibb.co]

The list of nicknames is restored if you go to any other window from the list of open windows "Switchbar". The rest of the bugs in "Menubar" remain in place.
For the testing, I am not using any pre-installed scripts or DLLs, so this cannot affect so that cause this bug. This is a new clean version of the mIRC client.

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