FWIW. That was the advice of Symantec Technical Support. It was the second time in a week that they had suggested reverting to NIS08. If I had listened the first time, it would have saved me as lot of grief, since I ultimately came to the same conclusion as jeremyT. The only way to fix NIS09 sharing problems is to revert to NIS08.
For the record, the problems were on a small (3 computers) Windows XP SP3 peer-to-peer network, and I did try: turning off Automatic File/Printer Sharing Control in NIS09; uncheck Use simple file sharing in Windows; JohnL’s setup remote monitoring on all computers to always on; made sure Windows firewall is off; set Trust Level to Full Trust; and turn off firewall, IPS, Advanced Protection, and Norton Tamper. Nothing worked. An hour or so after rebooting, the “server” (the computer the data files are kept on) would be unreachable (even though I could still ping it). I have reverted to NIS08 on the “server” and it has remained reachable since last night.
NIS09 remains on the two “client” computers, even though I am getting the 8920, 200 LiveUpdate error on them. If I have any more sharing problems I will revert to NIS08 on them also.
Hopefully Symantec will solve the problems with NIS before my subscriptions expire next October. ;)