I searched darkside portal and pyramid but can't seem to find this stoppage in play that is annoying me.

I just installed the game today, did some running around in Vertigo and Dwarf Mines, but whenever I enter any Darkside portal I get a "Press Ctrl + F4 + Enter" message in game text on the bottom.

Nothing happens when I push this combo and the game sits there, probably laughing at me. Is there a step in the troubleshooting I missed, running Windows 7 on most current updates.

Edit: To answer both questions below, I've only played using the speech mode option and as far as I can see, MM4-5 are installed together. The icon/shortcut is MM4-5 - World of Xeen - speech or non speech.
My save file is *.WOX extension, I'd imagine the game is complete Clouds/Dark.

Have you installed the entire World of Xeen (MM4+5 and extra content) correctly?

Are you running the original version or the "talkie" version? Both are now included in GOG's MM pack. Some players have had better luck running the "talkie" version, so you might try that.

Otherwise I'm not sure what would cause this. Anyone else have ideas?

You are playing the "full speech" (aka "talkie") version.

The speech originally came on 2 audio CDs, so, while playing, you would get a "change CD" message. The version on GoG contains 2 CD "images" with the message changed. The key combination is actually a DosBox hotkey combination to tell DosBox to virtually switch virtual audio CDs: -)

Try hitting the combination only once and waiting a few seconds for Xeen to recognize DosBox mounted the new CD. In some cases it has taken Xeen a while (10-15 seconds) to see the new CD while I have been playing.

This might be a silly thing to point out, but the combo is actually Ctrl+F4 release, then press Enter. Not the 3 keys together. That's what worked for me at least. And you might have to wait 5-10 secs.

Yes I have the same problem. For me spamming the ctrl + f4 + enter keys helped... ill try the ctrl + f4 -> release -> enter combo.

Thanks, I was simply impatient or hot hitting the sweet spot. It worked after a few seconds. Back to grinding!