multiple gnome sessions from same user

[Sam Folk-Williams]

Hi,

I'm noticing that if I have a gnome session on my desktop and try to
start vnc (which also uses gnome) as my same username, I get this error:

gnome-session: you're already running a session manager

iirc, in the past I would be able to open a second session as the same
user. Is there a reason/explanation behind not allowing multiple
sessions? Or have i configured something wrong?

thanks,
Sam