It may be that the e-mail you were trying to join with was of a type they might automatically reject.
I've had to do the same with the AmithlonOpen group because it was (and still is) being targetted by the spam brigade. It means a delay in signing up because I don't check on a daily basis, and in very rare cases genuine posters may get rejected because their e-mail is not obviously a genuine one.
In the worst case scenario, send me the question and I'll relay it to the AmigaSamba group for you.
