Spent the evening with:
Rearranging RAM modules because the SS10 would only blink the capslock LED after powering on ... until I remembered I had done an setenv diag-switch? true to do a full RAM test, and then it takes bloody ages for the screen to come up, and I was too impatient...
Fighting the RasterFlex card after reseating it into a different SBus slot - until I read the FAQ, which said that the drivers need to be uninstalled and reinstalled after a reboot -- -r so the internals get rearranged appropriately.
Now back to where I was this afternoon (except the RasterFlex does not seem all to spiffy in TrueColor mode after all, and also the screen blanks occasionally for some reason)...