update on this for anyone who is interested....
basically the issue was with icefaces.
I swapped to ajax4jsf for a few ajaxy bits and suddenly all the validation on the selectItems is now firing.
Looks like I will be staying with ajax4jsf, icefaces just doesn't seem ready for primetime what with this and the viewNumber exceeded exception...
We have logged this issue in the ICEfaces JIRA for investigation:
Note that ajax4jsf and ICEfaces are currently incompatible, so the presence of both Ajax implementations in the same project may be the source of the problem.
nope it wasn't actually.
initially I used icefaces... with no references to ajax4jsf. so i think its an icefaces specific thing.
anyhoo... .thanks for the response and logging a jira.