Returning to 1920x1080 problem.

After further investigation following the display problem I mentioned here I’m still finding a similar issue.
Using a number of programs installed from !PackMan. (Although I don’t feel the issue lies with !Packman at all.) If I run, usually games with sound, and decide to reduce the screen mode, using the display manager, to adjust the resolution to something more suitable to fill the screen and then quit the game. When I try to return the resolution to 1920×1080 16M colours, I get a black screen and mouse pointer. Power down reset neeeded.
!MineHunt and !Maestro don’t appear to have the same problem.
This was occurring in the pre-release versions when I think I’d got a basic 128/128 memory split.
Now with the official release version, ROM/Firmware update via !Packman, when I use gpu_mem=32 I still get the same issue. Not so with gpu_mem=64.
Tested with todays (12Nov) ROM and both June Farnell 256Mb RPi and July RS 256Mb RPi.
Is this something that can be (a) repeated or (b) fixed, or is the easy answer just to use more than 32Mb video for games!