Assuming that the network connectivity is stable and working properly between the SmartConsole and SMS, it sounds like a possible crash of the cpm and/or fwm processes on your SMS. Run cpwd_admin list on your SMS's, do you see a restart time for cpm/fwm that correlates to when the SmartConsole crash and lack of access occurs? If these processes are crashing, it normally takes about 5-10 minutes for them to reinitialize before you'll be able to successfully log back in to the SmartConsole.
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