[USR-TC] NMC keeps rebooting

one day i found that NMC was undable to respond to snmp queries (not ip problem - ping was ok). some problems had console too - very slow performance. after that i tried to configure from defaults (by dip #5) - console got ok, but same problem with snmp. i reflashed NMC with software version 5.4.1 now it is rebooting each time it loads. how to get it to work? can chassis work without nmc? ( Dual E1/R2, Quads, NETServer card - old chassis).