X was sending spurious mouse focus events when grabbing and ungrabbing
the mouse. This was causing CivCTP and RT2 to stop scrolling when the
user hit Alt-Enter. This is fixed in the latest SDL CVS.–
-Sam Lantinga, Lead Programmer, Loki Entertainment Software
It hadn’t come up before since no OpenGL game we wrote was able to
iconify itself from within the game, but I just fixed a bug in which if
you have the cursor hidden and the input grabbed, and you iconified the
game by a keybinding, then DGA would stay enabled, preventing you from
moving the mouse. This is fixed in SDL 1.1.5 CVS.
Along similar lines, if your game will never need the precision of DGA
mouse, and you hide the cursor and grab the input, then you can prevent
SDL from ever using DGA mouse by setting the following code before you
hide and grab the mouse:
// Disable SDL’s use of DGA since we won’t need it at any time
putenv(“SDL_VIDEO_X11_DGAMOUSE=0”);
This isn’t the case for Myth2, BTW. 
See ya!–
-Sam Lantinga, Lead Programmer, Loki Entertainment Software