hi there.

When i log in windows with rdesktop everything works fine,   when  a image shows up on the screen (like picture of a site, opening a image file, or image preview) , the screen updates get really slow and it freezes.

Only the screen freeze, the system can send mouse and keyboard output, if i login with another machine i can see that the ctrl+alt+del opened the task manager.

I tried different options  and combinations but no luck .
-0 -4 -5  -P -z -b -a (8,16,24) -x m -g800x600

OBS : i have this problem only when connecting from a sis machine to a windows 2003 server,  rdesktop to windows xp works fine even with the sis chipset. 

my server 
os windows 2003

my client 01  
os : ltsp 4.2.u2-0
rdesktop :  1.7
vga : sis 550
eth  : rtl-8139

my client 02
os         :  ubuntu 10.04.3
rdesktop:  1.6.0-2ubuntu3.1
vga : sis 65x/M650/740
eth  :SiS900

any help would be appreciated.