Cannot use CTRL+8 in linux

I'm using Juce v3.0.7-41.  I have a juce application I'm writing that uses CTRL+1, CTRL+2, CTRL+3, etc... as hotkeys.  This all works well in Windows.

When I compile the same application for linux (64-bit Ubuntu 14.04) I cannot get CTRL+8 to work.  The keys are all defined the same way in my application:

KeyPress CTRL_6 = KeyPress::createFromDescription( "CTRL + 6" );  ///< Switch to the 6th open order.
KeyPress CTRL_7 = KeyPress::createFromDescription( "CTRL + 7" );  ///< Switch to the 7th open order.
KeyPress CTRL_8 = KeyPress::createFromDescription( "CTRL + 8" );  ///< Switch to the 8th open order.
KeyPress CTRL_9 = KeyPress::createFromDescription( "CTRL + 9" );  ///< Switch to the 9th open order.

In my keyPressed() method inherited from KeyListener, I've added a printf() to see when it gets called, and it gets called for every CTRL+1, CTRL+2, etc..., combination with the exception of CTRL+8.  Just that one is somehow consumed.

Does this ring a bell?  Anyone know why CTRL+8 on linux would be handled differently from the other keys?

could it be that your window manager or some other application is grabbing the key?

if you set it as a shortcut in a regular linux app, does it work?