Patrick> There is a known bug regarding hanging NDMP sessions and this Patrick> ontap version. Upgrade to the P2 version and your issue Patrick> should be resolved
Thanks for the info, though in my case I'm not sure if that's completely the issue, since it looks like the NDMP session(s) tend to go away properly, but the backup sessions don't terminate properly, which leads to NDMP failures when they can't allocate new backup sessions.
In any case, I'll login to NOW and see what I can find in terms of the changes between 7.2.6.1 and 7.2.6.1P2 that relate to NDMP.
Thanks! John