You are not alone.
Please read this:
It would help if you gave some more information eg have you got an ADSl or FTTC line, what system/ browser you are usiing ...
Has worked first time every time for me since it superceded speedtest.bt.com a good few weeks agon and was upgraded a few days ago.
Are you using a PC ? What vesion of Windows and browser ? Is flash player up to date ?
have you tried using firefox or IE8?
I think that all the testers have had occasional blips with the part that gives profile speeds. For some people, those 'blips' seem to have lasted a month or more. I guess (not sure) that this is something in the back end information, and the same for all the different testers.
Hi, a few of us suffered this last year as stated in the other thread linked.
It happened for just over 2 months for me, no explanation was given and is still being looked into (so I am told).