Apparently PRTG's implementation of SNMP is causing Cisco SG300's to stop responding on HTTPS. In my experience this issue also causes the switch to have problems when a reload command is issued and eventually you just have to pull the plug.
I still have an open case with Cisco but they seem to be implying its Paesslers problem so I thought I would open a case here as well. Is this a know problem and is there a fix? I have a lot of these switches currently effected by this issue.