Can't load Screen.dll

1
Hey!

I have a problem with screen.dll. Sometimes I can't run my program-
file on my experimental PC (Windows, 166 MHz, 126 MB Ram).
Matlab posts the following message:

Unable to load mex file: C:\Programme\Matlab6-1
\toolbox\PsychToolbox\PsychBasic\Screen.dll.
Eine DLL-Initialisierungsroutine ist fehlgeschlagen.
??? Invalid MEX-file
Error in ==> C:\Programme\Matlab6-1
\toolbox\PsychToolbox\PsychOneLiners\BlackIndex.m
On line 30 ==> PixelSize=SCREEN
(windowPtrOrScreenNumber,'PixelSize');
Error in ==> C:\Programme\Matlab6-1\work\exp_21_1.m
On line 4 ==> black=BlackIndex(screenNumber);


It's always working perfect on my home PC, but just every once in a
while on the experimental computer.
I don't have a clue if I have to change some settings, if the screen
file has a bug or if the PC is too slow?! What completly confuses me
is that the error doesn't appear every time! It doesn't have
anything to do with my program file, because if I just try to start
the screen file in the command window, it's not working either!

Thank's a lot for any suggestions!

Best wishes,

Timo