More Dial Up/ISDN problems (Fast4.net)

[AMDX23800+]

Hi,
I recently switched to unlimited dial up/ISDN for £6.99 from www.fast4.net.
It has been working fine until today, it disconnected and when i tried to reconnect it said 'Check username and password' and it hasnt worked since.
I have tried retyping my username and password several times with no luck, i know they are correct.
Does anyone else have fast4? (I'm thinking it's a problem at their end)
Any suggestions would be great
Thanks

Edit: This is exactly what comes up :
'Checking initial state ... Ok
Checking ISDN ... Ready
Connecting with ISDN ... Connected
PPP negotiation ... Success
Authentication ...
Authentication failed. Check your PPP usernames and passwords. '
It worked fine before and i haven't changed anything

 

[AMDX23800+]

It seems to lose the connection before it actually gets to the authentication step.
It connects for like 1 second and then loses connection straight away (before its had chance to check the password and username).
When i click dial, the B1 channel light comes up on my router and then goes off again straight straight away.
Any ideas?
Also, i tried one of those 'Free ISP' numbers with name:connect pass:connect (0845) and that worked fine. Why has my Fast4 0808 account just suddenly stopped connecting?

 

[AMDX23800+]

I rang their 'Server status line' and it said 'no problems with servers on Friday 28th April' . So i suppose they went down on Saturday and no one has been there to fix it?
Their site works still.