Problem with CrossOver Games & X11 on Yosemite

Hello everyone, I'm having an issue that I haven't yet been able to resolve using the information I've found on the web. I have a MacBook Air running Yosemite 10.10.4, and I'd like to play a game called Terrordrome, which I'm told requires the software Crossover Games to work on a Mac. I've installed it, but whenever I try to install the game itself I get the error message,

"CrossOver Games cannot run because a required system component, X11, is not installed."

In response I've followed the advice given elsewhere and have installed the latest version of XQuartz (from this website: http://xquartz.macosforge.org/landing/). I've seen that it includes the component X11 (2.7.7, the latest version). Yet when I now try to run Terrordrome (after logging out of my account and in again), I still get the exact same error message from CrossOver Games (though first the system tells me that COG quit unexpectedly). I don't get what's happening as clearly X11 is already installed on my computer.

Some more details about my computer:

Processor: 1.6 GHz Intel Core i5

Memory: 4 GB 1600 MHz DDR3.

Still got 73 GB of storage free out of 120.

Anyone knows how I should go about solving this problem?

Many thanks in advance

Alex@ndros