Just a WAG, Rolf, but do you have option 67 set on your DHCP server? Because, it would seem, the SG300 loads whatever file you have defined by option 67, and tries to parse it as a configuration file. Now, in my case, that file (which is the defaul...
I'm having the same issue as the OP on a brand new SG300-28 (unboxed today). Attempts to save any changes -- as simple as the password after a "fresh" reset (via pinhole or web UI) -- result in "Another copy process is active, please try again later...