cannot search for new themes

I have many wordpress sites on which until today I was happily going about wordpressing. Today I went to change the theme on one of my sites and found that I can no longer search for themes. I get a “unknown error” when I put in a search term and the check boxes and descriptions for the search options have completely disappeared. This is happening on all of my wordpress sites. Has anyone heard of this? Has anyone got a clue what is wrong and how to fix it?

I even went so far as to completely remove wordpress (including the database) from one site and performed a completely new basic install. I still have the problem on that site.

I also went to my support for my hosting and they could see the problem, but blamed it on wordpress rather than looking for a possible cause on their end.

ANY help is appreciated.

Thanks,
Dawn