Are you using paid version?
I'm using paid version. Since last week I've been having all sorts of problem with MS. Mostly with the "Retry Limit Exceeded" issues that the MS support claimed they have fixed, but somehow yesterday I still had that problem. Although, this morning the keyword tool works fine.
I've been searching on their forums and it seems like I'm the only one having this issue, with the last thread about retry limit exceeded was about a nearly a month ago (early nov).
If they can't fix this I'm switching to monthly payment based keyword tools like keyword country or even IM eye. I'm so sick using Google Keyword Tool with no filtering options like in MS.