Bug#249811: this sounds like an X problem to me

[Sean Burlington <sean@uncertainty.org.uk>]

Josh Metzler wrote:
> What video card is in this box?  If the XFree86 video driver supports it, 
> try setting the software cursor option:
>
> in the device section of /etc/X11/XF86Config-4, put
>
> Option "SWCursor" on
>
> I hope this helps,
> Josh


yes this fixes the problem - thanks :)

the video card is integrated with the motherboard (ASUS P4S800-MX)

the manual describes the video as

SiS Real256E integrated graphics

from /proc/pci


PCI devices found:
  Bus  0, device   0, function  0:
    Host bridge: PCI device 1039:0661 (Silicon Integrated Systems [SiS])


    VGA compatible controller: PCI device 1039:6330 (Silicon Integrated 
Systems [SiS]) (rev 0).
      IRQ 11.
      Prefetchable 32 bit memory at 0xf0000000 [0xf7ffffff].
      Non-prefetchable 32 bit memory at 0xe7800000 [0xe781ffff].
      I/O at 0xd800 [0xd87f].