there is -nothing- in the SDL code to suggest -why- the mouse is jumping
around on me. The only thing suggested in the gpm code is that the
sampling rate when out sometimes gets invalid dx/dy values…
I hope this helps because I have -no- idea -where- the sampling rate is
set. Still hunting…
although gpm does -not- have support for wheel or additional data… I
don’t think that makes any difference because packetsize is fixed.
G’day, eh? 
- Teunis
PS: this affects -all- SDL programs that run under fb and use a mouse. So
it’s definitely a mouse issue… and as both gpm and X work fine, it’s
not a prob in the mouse itself…