This issue is seen only if there is some SNMP configuration on the switch.
When the configuration is saved with the write memory command, free space in NVRAM decreases continuously. This issue can be observed with the dirnvram command. 1024 bytes are lost every time the write memory command is issued. If the command is repeated until there is no free NVRAM, this warning is displayed by the switch:
% Warning: Saving this config to nvram may corrupt any network management or security files stored at the end of nvram.
This issue is documented in Cisco bug ID CSCeb45692.
When this error statement is hit, choose yes. The user-config is then saved, and there is an internal cleanup. If the dir nvram command is issued now, the original free NVRAM value is displayed.
As an alternative, upgrade to Cisco IOS version 12.1(20)EA1. In order to obtain this software, go to LAN Switching Software.