NSWmodellers problem sounds exactly like mine, however do you have an explanation as to why my loco would work perfectly on the SPROG II and not the layout?
NSWmodeller, have you a SPROG II or do you program on the layout?
Also to NSW modeller...
Does the model have those twin caps attached?
Does the motor turn when regular DC is applied to the rails?
Check values of CV 3 (accel CV). If it's at a maximum, the loco will take a minute to move.
Check value of CV 29 (directional bit).
Though it does sound as though you've not mucked around with CVs ex factory, so it should just work.
I've found on O scale models the massive motor cap can stop the motor from moving at all. I understand that the caps work ok with the Powerline decoder, but it may be worth disconnecting them if relevant to the 48 class. The LS decoder will come with noise suppresion hardware on it anyway. Also, that fan and light board may be worth disconnecting too - I reckon it muddles with decoder programming. This issue is a little strange, as there's absolutely no signal getting to the motor by the sounds of it.
I don't use an SPROG programmer or Select decoders much, but it may also be worth asking questions on the Yahoo Groups LokSound forum.