DVD Locking!

We have a problem with a Artec DVD 12X with a Riva TNT M64, 128MB. The MB is Jetway's J663AS with on-board sound.

The Problem:

Ranging between 8 - 20 minutes in to the DVD Film the player locks. The system doesnt crash, but we have to ctrl,alt,delete to get back to desktop.

Solutions tried Upto Now (And still trying):

Newwest VGA Drivers
Disabled on-board sound
Disabled EVERYTHING in Startup (MSCONFIG)
Disabled Screensavers and Standby modes
Tried other DVD`s
Tried other DVD software players

We are going to test the DVD Drive out of the system, try the system with clean install of win98

have you enabled dma mode in properties?

check to see if DMA is turned on for the dvd drive if it is, try turning it off, if it is off turn it on.

DMA has always been enabled during testing, we shall try it with out DMA

DMA is disabled and it still hangs, NEXT!

Thanks anyway for suggestion

what speed processor is it running and how hot is it getting?
can you make it lock anyother way? (easy test is run a timedemo in quake2 and let it loop, or run a 3d benchmark in loop mode)

The processor is a Duron 700 it runs at about 34 Degrees. Ill let you know if anything else locks the system as we testing it now.
P.S Please keep coming with these ideas as we are really stuck.

has the unit been tested with another dvd drive? does a regular data cd read fine and not lockup when you try to copy the contents to the hard drive? have you tried a diff video card? (new one or diff model)