Question about VESA for professionals

Hello,
i have discovered an interesting thing:

i have used VESA setmode via BIOS function:

Code:

bsetvesamode: ; bx=mode number
 mov ax,4f02h  ;set vesa 1.0 screen mode
 int 10h
 mov ax,4f05h    ;vesa 1 window select
 xor bx,bx
 xor dx,dx      ; set bank 0
 int 10h        ;dx is  the reqired bank
ret

where bx = input desired video mode
was $13 - a standard mode

then i was putting random pixels to screen

the problem was when i wanted to press Print Screen button,
result: immediate hardware reset under win98 se

when setmode like this:

Code:

mov ax,$13
int 10h

Print Screen is working

could someone tell a reason?

MATRIX