I have successfully activated multisite and added the network admin panel to my dashboard, but when I create sites I get a basic 'site not found' page when i try to 'visit' them or go to the dashboard.
Backstory - I upgraded to to 3.5 today on this domain that I've hardly worked on and decided to activate multisite before continuing to work on it. So this was not a fresh installation, but not something I cared about loosing.
I followed the instructions and the network admin was successfully added to my dashboard.
*It only allowed me to do a subdomain setup (which was what I wanted anyway but thought it worth mentioning in case it helps solve the problem)
Any guidance would be much appreciated