Modules and admin theme stopped working

I have a huge problem that needs resolving or needed resolving five minutes ago...

First I have the nf_registration module which makes the user choose a role before registering i.e. when you click create new account your redirected to a page with a drop down to choose which type of account you want. When the user have selected role he's sent to the registration form and afterwards to a special pageroute for that role. Now for some reason this has stopped working I have done nothing with module and a local copy on my server is working perfect thus it seems to be a server problem at my host that is creating the problem. My hunches are: memory low(but that is usually reported by drupal), high load I have cirka 2000 unique users per day so that shoudn't be to much of a problem, some server settings. Anyone had the same type of problem maybe not to do with nf_registration module but something similar.

My second problem is that once I submit info on any of the administration pages the admin is changed to the default theme. A click on the reload button makes the admin theme reappear.

Now I think these problemes are related in some way. If someone could give some pointers as to what might be wrong or help me fix I'd be more than thankful and I kind of need the answer in a hurry!