what does this BSOD BugCheck actually mean?

I'm working on a system that always BSOD in a couple of games, but
only in certain situations.
First, the situation, then what I've done, and finally, the output of
the BugCheck.
(I'm really hoping there's some answer in the BugCheck I'm missing.)

For example, in Battlefield 2, whenever one tries to Alt+Tab out of
the game, it always BSOD. Or, if played long enough, (say, an hour) it
will often BSOD unprovoked.

This ONLY happens in this configuration:
When using the ATI 2600XT PCI-x video card on the SATA drive.
If I use the onboard NVidia video chip, can't get it to crash.
If I use the IDE drive, with the exact same WinXP Pro install, and
updates, and drivers, etc, no crash.
And obviously, NVidia chip and IDE drive, no crash.
Only ATI card and SATA drive.

What I've done:
Tested the RAM with memtest86+: no probs. Tried running with one RAM
stick, then the other, and in different slots, still crashes.
Drivers: Used every one possible: provided on CD, available from
Windows Update, two different Catalyst versions.
HD: scandisk, badblocks, chkdsk, PartitionMagic error check--all
passes.
Tried swapping SATA cable and using different port on mobo, still
crashes.

Oddity: At one point in all this, the ONLY time I couldn't get it to
crash while using the ATI card and SATA drive, is when I didn't
install any of the sound drivers (not Realtek, not the Microsoft High
Def' Audio Bus, etc.) May be a fluke.

Anyway, here's the BugCheck. Is there some deffinite answer in here
I'm totally missing?
Thanks for any feedback!


*******************************************************************************
*
*
* Bugcheck
Analysis *
*
*
*******************************************************************************

Use !analyze -v to get detailed debugging information.

BugCheck 10000050, {e1a7e304, 0, bf89412b, 1}

Could not read faulting driver name

Probably caused by : win32k.sys ( win32k!WatchdogDrvGetDirectDrawInfo
+b1 )

Followup: MachineOwner
---------

0: kd> !analyze -v
*******************************************************************************
*
*
* Bugcheck
Analysis *
*
*
*******************************************************************************

PAGE_FAULT_IN_NONPAGED_AREA (50)
Invalid system memory was referenced. This cannot be protected by
try-
except,
it must be protected by a Probe. Typically the address is just plain
bad or it
is pointing at freed memory.
Arguments:
Arg1: e1a7e304, memory referenced.
Arg2: 00000000, value 0 = read operation, 1 = write operation.
Arg3: bf89412b, If non-zero, the instruction address which referenced
the bad memory
address.
Arg4: 00000001, (reserved)

Debugging Details:
------------------

Could not read faulting driver name

READ_ADDRESS: e1a7e304

FAULTING_IP:
win32k!WatchdogDrvGetDirectDrawInfo+b1
bf89412b 8b0e mov ecx,dword ptr [esi]

MM_INTERNAL_CODE: 1

CUSTOMER_CRASH_COUNT: 1

DEFAULT_BUCKET_ID: DRIVER_FAULT

BUGCHECK_STR: 0x50

PROCESS_NAME: BF2.exe

LAST_CONTROL_TRANSFER: from bf008af2 to bf89412b

STACK_TEXT:
ab51c3b0 bf008af2 e5ce1080 e8f16a24 ab51c3ec win32k!
WatchdogDrvGetDirectDrawInfo+0xb1
ab51c3f8 bf009033 00000001 e79bf798 ab51c480 dxg!vDdEnableDriver+0x8a
ab51c414 bf876ded e8f162d8 00000001 e13dc2d8 dxg!DxDdEnableDirectDraw
+0xbf
ab51c434 bf89173d ab51c5d4 e1802f68 00000000 win32k!
PDEVOBJ::bMakeSurface+0xe2
ab51c460 bf89213d e1802f68 e1a60270 e895c6f8 win32k!hCreateHDEV+0x3a9
ab51c5d8 bf898a80 ab51c6a0 00000000 00000001 win32k!DrvCreateMDEV
+0x4dc
ab51c6cc bf89ace5 ab51c6a0 e3fb0008 00000000 win32k!
DrvChangeDisplaySettings+0x251
ab51c710 bf89abd8 0012f9f4 00000000 00000000 win32k!
xxxUserChangeDisplaySettings+0x141
ab51c738 8054086c 0012f9f4 00000000 00000000 win32k!
NtUserChangeDisplaySettings+0x4a
ab51c738 7c90eb94 0012f9f4 00000000 00000000 nt!KiFastCallEntry+0xfc
WARNING: Frame IP not in any known module. Following frames may be
wrong.
0012f9fc 00000000 00000000 00000000 00000000 0x7c90eb94

STACK_COMMAND: kb

FOLLOWUP_IP:
win32k!WatchdogDrvGetDirectDrawInfo+b1
bf89412b 8b0e mov ecx,dword ptr [esi]

SYMBOL_STACK_INDEX: 0

SYMBOL_NAME: win32k!WatchdogDrvGetDirectDrawInfo+b1

FOLLOWUP_NAME: MachineOwner

MODULE_NAME: win32k

IMAGE_NAME: win32k.sys

DEBUG_FLR_IMAGE_TIMESTAMP: 45f013f6

FAILURE_BUCKET_ID: 0x50_win32k!WatchdogDrvGetDirectDrawInfo+b1

BUCKET_ID: 0x50_win32k!WatchdogDrvGetDirectDrawInfo+b1

Followup: MachineOwner
---------