UASD BCT15 Can't add channels

[CommRX]

A strange problem has just appeared on UASD. While programming a conventional system with 5 groups, it will not allow me to add channels to 2 of the groups. Only 31 percent of the memory is being used on the BCT15, so I know it is not full. Any ideas? I can delete the group, and create a new one, but when I switch tabs, the "New Channel" option is grayed out. Is there a channel limitation? (531 in this case)