Doesn't look like anything close to a clean dosbox.conf.

it's a known nvidia SDL 8-bit color issue, my geforce2 and fx did this. If it involves constant smooth palette changes in real time it will be slow in 8-bit on an nvidia card.

Woody,
I removed the VSync section in the conf file, this was due to a bug in D.O.G. 1.54 beta. Thanks,

Now I start DOSBox using the attached conf file. Fullscreen is on.

To reproduce :
Start Quake 1.0.1 and let the menu demo play out in fullscreen until the player gets to the portal door.
ALT+Enter to window mode and back to fullscreen before the player takes the golden-key and shoots the zombies that pop out from under the water.

The game in most cases results in a slow drawing of the flash (from the golden-key) and distorted visuals.

Some missing data from my first post :
Windows Vista Business without Aero.
ATI Mobility 9000

One sidenote though,
The mixer cdaudio part in the conf, I got that from somebody on the net that this controls the volume of the cd if using mount D D:\ -t cdrom.
Is this true, I tried it and it doesn't work for me?

Erik.

Please start with a clean dosbox.conf and change values until this
issue happens, to isolate the switches that cause it.

Started DOSBox using a fresh config file. Only adding an autoexec to it. See attachments.

Same scenario is valid. Alt+Entering and Surface cause the drawing.

Running the game from the start in fullscreen or window won't cause the drawing. Switching between window or fullscreen while running the menu demo (Haven't tried while playing) will cause the drawing.

Will test on an XP system (ATI x300) tomorrow.

Erik.