Black screen after launching

I originally posted this in the BtS section but it really ought to be here, as I've now discovered the same problem is affecting Vanilla (1.74) and Warlords.

I've just installed the BtS 3.17 patch and am faced with a black screen upon launching. No menu, no nothing. Except that the taskbar at the bottom of the screen tells me that BtS is running.

I'll have a play around with it, but can anyone guess what the problem might be? I never had this before.

Changing the screen resolution doesn't help, and in any case the unpatched version was working perfectly well with the original resolution. BtS starts up OK - I get the progress bar showing everything launching - but once the launch procedure is finished, I'm just presented with a black screen.

[One other strange thing: although I definitely downloaded the 3.17 patch, when I click on 'Properties' on the application's icon, it shows as version 3.1.3.1!]

My specs: Intel Mac Pro, 3GHz dual-core Xeon, 4GB RAM, ATI Radeon HD 3870, running Windows XP with SP2 via BootCamp. The Windows partition is completely separate from the Mac partition and is used solely for BtS. Video drivers are up to date.

DirectX Diagnostic information is attached; I don't know how to read these things, but nothing leaps out as obviously a problem.

Many thanks in advance for people's help.

Problem solved!

Since I was running two monitors, I simply disconnected one monitor to see if that made a difference. The game launched OK and I was able to get into the menu. Then I discovered that the patch had reverted to the default screen resolution. I changed the resolution to my monitor's setting (1920x1200), and bingo! No more black screen! Reconnecting the second monitor made no difference - I was still able to launch BtS successfully.

I can't get the Diversica mod to work, but that's a problem for another thread...