Just what I was looking for!
When I switched back to my 2.6.11 buildroot, I started getting the "no touchscreen" message, and I couldn't remember what the magic bullet was!  I tried diffing everything, thinking there was something in tinyx's  config/cf that I'd played with, etc.   Forgot that I'd done the ln -s /dev/nul /dev/ts as suggested by Bhaskar.
So, if i make a soft link in the buildroot/root/dev/ts to /buildroot/root/dev/null  will it persist when I flash the gumstix next time?  If so, I'll add that to my version of the tinyx Makefile to avoid forgetting that step again.
A mind is a terrible thing to loose,
Dave Thomas