Cannot launch game with directx 11

I installed the game a couple of days ago and spent a few minutes happily exploring menus in the game in dx 11 mode. I exited and since then haven't been able to get back into the game. When I click on the civ v or steam icon I am prompted to choose dx 9 or dx 10/11 (recommended). I choose the latter, the prompt disappears and then - zilch. I've tried adjusting steam's compatibility mode unsuccessfully. I've got the latest drivers. My spec is i7. 4 Ram, ati hd 5770, windows 7, 64 bit. So plenty good enough. It's very frustrating. When installing the game I switched from the suggested Drive C to D and have since read that this can confuse steam. Anyone know if this is likely to be the problem and I should reinstall on the C Drive? Any other suggestions?

Have you tried launching it by double-clicking the actual exe file? Also, check the game folder and in Event Viewer for any crash logs.

My Steam install is on drive E and I haven't had any issues with it.

Yes, I tried launching the game from the exe file without success. I'm afraid I can't find the event viewer.

Have you tried just launching in DirectX 9. My machine is also up to recommended specs and will not run in 10/11 mode, but I have no problem in 9.

Yes, I've tried launching in dx 9. It takes me to the game but the mouse cursor is invisible and the graphics, which were all 'high' the one time I was able to start the game in dx 11, are on low or medium settings.

Okay, by right clicking on the game in steam and going to 'local files', I got the cache verified successfully. A download then started (I know not what) and when it had finished I was able to start the game at last in dx 11 mode. BUT the mouse cursor is invisible! It highlights tabs as I move it about the game menu page but it is invisible. Does anyone know how I solve this latest problem??

I've now managed to get the mouse working properly by unchecking 'fullscreen' in the video options menu. So far I am able to play the game at last. Anyone else play with fullscreen unchecked? Any known problems? (I'm paranoid after all the trouble I've had just getting this game to work!)