rushing KbWait function failure with Windows XP?

1
Hi,
I have tried to run this code on several XP and Win98 computers. For
all XP computers but one, the PC seems to hang (only a hard restart
will help).
All computers find a "prioritylevel" of 2 for this code. Setting
"prioritylevel= 1" would solve the problem. Does anybody know
what's going on here?

paul


function Test_rush1
clear all;
warning off MATLAB:DeprecatedLogicalAPI;
screenNumber=0;
window=Screen(screenNumber,'OpenWindow');

loop={'Screen(window,''WaitBlanking''); '
'begin=GetSecs; '
'WaitSecs(1); '
'Screen(window,''WaitBlanking''); '
'eind=KbWait '};

priorityLevel=MaxPriority(screenNumber,['WaitBlanking'],['WaitSecs'],
['GetSecs'],['KbCheck'],['KbWait']);
Rush(loop,priorityLevel);
Screen('CloseAll');