a blogger question

Can anyone explain to me the reason for this problem I've been having lately? Whether you write the link http://infavorofthinking.blogspot.com or http://www.infavorofthinking.blogspot.com, it should work either way. But lately sometimes I'm having problems with the links without the "www" -- for my own and other Blogger sites. I get an error box that says "the file is not available on this server." From within Blogger, for instance, after I post, if I click on View your Blog, I get the error.
I'm using Firefox, if that makes any difference.

would appreciate any ideas. I can work around it, by changing the format of my links etc. But it's irritating.