How do I fix my broadband connection?

I'm not easily stumped when it comes to the net, but this is a real hair-tearer. Yesterday I had to get my broadband re-installed cuz of various reasons, and now that it's working properly I can only access it from my account and not my mum's or guest's or grandfather's...i've created shortcuts in each account but every time i double-click on them it says 'broadband connection can not be found',and in my acc. it works perfectly fine! when i'm already online and i switch users it disconnects automatically!

i've been up since 3 in the morning (it's 6:15 am now) trying to fix it and my desk is overflowing with disposable coffee cups and luckily it's weekend out here, so pls help!