Try switching your router/modem off and give it 30 secs to a minute and switch it back on - sometimes a simple reset can sort it out.
If that doesn't do it, then check to see what programmes you have running, something may be trying to update itself without telling you. Run a virus check, spyware check and do a disk defrag - usually more useful if the computer itself is slow, but it never hurts to do one anyway.
If you get no joy from that then it could be a problem with the phone lines in the area, Supanet's servers could be having some maintenance especially at the time you're posting.
If you're sure it's not your machine, run some speed checks, google "broadband speed check" and see what it comes up with. if it's way below what you usually get, then at least you have something to take to Supanet and get them to look at it.
Hope that helps