To me it sounds like a similar issue to what is mentioned in this thread:
The workaround proposed from Winter Rat is to “press Ctrl+W then “Cancel” and it responds again”.
Hope this helps…
I’ve been experiencing occasional mouse GUI lock-ups… for me, clicking on the desktop and then back to C7 frees it up again. I had figured it was some bug introduced with the new mixer as I hadn’t had this in C6.5
EXACTLY! Now that you say that I can clearly remember me picking a VSTi from the list, then pressing cancel and Cubase froze. Thank you for this, it’s also good to see this is on the bug list.
I will also try the solution to see if it works next time this happens.
The next update is due the beginning of Feb so hopefully! I’m not counting my chickens though.
In my case no. Separate output for DAW and Windows.
Me too! Only occasionally - happens with 6.5 as well.
If I minimise Cubase to the taskbar, then click on the minimised icon to unminimise?? (Whats the correct word for that?)
all goes back to normal.
I suspect that this post I made is related, although nobody else seems to have the same problem.
http://www.steinberg.net/forum/viewtopic.php?f=184&t=33017
Buzz
That does not work for me. In fact I have yet to find a way to get things going again without closing and re-booting Cubase. Luckily I am still able to save before closing. You know it is almost like a window is open waiting for a response and hidden under Cubase.
I was a bit confused about what you meant by a signature track?
Minimizing and restoring does not work for me either 
Thanks Emotive - my brain is old and tired!
@ Silhouette - Signature track = 3/4 4/4 6/8 etc
Right click in track list - add signature track
Buzz
But not as tired or as old as mine!
Thanks
Issue confirmed here aswell, the same way you described it. When cancelling an “Add Instrument Track”-window Cubase 7 always freeze for me.
But I haven’t got the Ctrl+W-trick to work (maybe because there has been nothing to save yet, those times I’ve tried it?!)
And why has the other thread about this issue been locked?
I had a quiet weekend, so decided to start everything again - Format C drive and clean Windows 7 64 install. (With SP1)
Worked all day Sunday, and problems have not ocurred again.
Buzz
Yah, thats what happens here when i edit the remote control editor and rightclick any knob… If i open anything in taskbar or so, i am able to close it… If i dont open anything else, its frozen (but still playing music;) )
I had this issue with v6.0.7, still persisting into 7.0.1.
It’s not a workflow-killer. I just minimize the Cubase window and maximize it again, everything is refreshed and good to go. Happens maybe once or twice per session, and generally only when I start / stop to preview some MIDI.
This is also happening to me as well–but I think it may be linked to me having a dialogue waiting for input. Unfortunately though, the dialog window is never on the top of my screen and can’t be found via alt-tabbing so I basically have to save the project with a keyboard shortcut, then restart Cubase to fix it.
I’ve only noticed this occurring since I’ve moved to Cubase 7, it never happened before for me on 5.5. Very frustrating!!
Yes it happened to me also a couple of times.
I hope it gets fixed in the forthcoming update
This happened to us today using a low buffer setting. Increasing the sive of the buffer solved the problem. 
Same thing happens here. 7.0.3 Mac version. I can recreate by dragging in an audio file from OSX Finder. GUI (except menus) freezes and cannot be “unfrozen”. Cubase can, however, be closed the normal way. Audio interface: UR28M.
I have a similar problem that is random but duplicated using my onboard video card, a PCIe Nivida and ATI video card.
I get random mixconsole lockups only when I add a third monitor to the scenario. This even happens when I disable the onboard video and use the ATI card which is Quad view card. The random problem involves the mixconsole (always displayed on monitor 2 in full screen mode) screen freezing like a photo while I have complete control of the project screen on monitor 1 and monitor 3 which always has the internal EQ screen, the floating transport and my opened plugins. Sometimes when mixconsole freezes so does the floating transport and the EQ screen…sometimes not… sometimes the floating transport will freeze but not the mixconsole. It’s a damn mystery and I’ve tried everything. Latest drivers, BIOS. tried 3 different video cards. I don’t know if it happens in 6.5 because I never went past 2 video displays. This ONLY happens when I add a third display! Oh… and to fix the freeze when it happens is to either close the Mixconsole screen and reopen it with the F3 key or just minimize/maximize Cubase…WIERD!!!