the interface is unknown/rpc server is unavailable/

I wonder if anyone out there can help me,
I’m having a serious problem with my Pc.
It all just happened out of the blue.
I will explain the symptoms.

When I switch my computer on and try to click on a program, I get one of the following errors:
the interface is unknown or
rpc server is unavailable
I can’t access my computer, any files or any internet connection.

I’ve tried a system restore with my Win 7 disc which didn’t work
I tried repairing it with my Win 7 disc and the first time it worked.
I managed to get on and do everything I needed.
Once reset the whole thing started again, but this time with the following error::
user profile server failed to login.

So I reset and it starts up and goes back to a vicious loop whereby I get the interface is unknown or rpc server is unavailable, if I try to do something it usually restarts itself or if I leave it, it restarts around 10 minutes later.
After about the 5th or 6th restart. it's back to normal, only to start the loop all over again after the next shut down/reset

The Win 7 disk won’t repair it any more.
Bare in mind it starts ok in safe mode, but I haven’t installed anything new or made any changes in a while, so I don’t know what I’m looking for.
Does anyone have a solution?