When I type a lowercase "q" in any program on the Parallels side of my iMac, the parallels desktop disappears, and all of the open program windows appear to be floating in front of the Mac desktop (the Parallels icon in the dock still appears to be active). When I type lowercase "q" again, the parallels desktop reappears with the program windows inside of it. The lowercase q does not ever appear in the fields I'm trying to type within, it just causes the actions described above. Uppercase Q and all other letters work just fine. What's going on?
Sounds like q is activating and deactivating the "Coherence" feature of parallels. Check the parallels preferences for a hot-key assignment. In Coherence, the desktops are merged as you describe.