its a server problem not linked to whether you are member or non member. The one good thing about swapping to vb is that they can get support from vb so should be able to work out how to configure the server correctly, the old xmb never really offered that. They've resolved some issues on viewing sections before it went down again today.
also with vb they could configure it to stop guests accessing the forums if the problem is linked to the number of connections, that would allow members to use it.
You need to be a member to do sigs, i don't know about avatars.