When you try to do something, very frequently, you may find you are unsuccessful and Blogger gives an error message. There is a long list of error possible messages and it is hard to keep track of them. You can try posting problem to Google Help group and to contact Blogger support or Blogger support 2
Update 2008: You can now only contact Blogger Support on account related matters. For error codes, please report your error codes at Blogger error code reporting form and a human from Blogger is supposed to look into the problem and try to fix it although they will not respond to your report. For me, I will do this as well as try what is described belowL
It will not be easy, but from feedback, bloggers have got helped, one within a day of getting through to Blogger support.
I have ignored error messages before and tried again AND succeeded.
Other thing you can try - use a different browser. It may or may not help depending on the cause, but that has helped me through many diffferent difficulties. Once you have the browsers in your computer it is very easy to do.
Others have recommended clearing cache and cookies, Me, I prefer to do that when I chose and not when I am forced to, to leave that as a last resort because clearing cache and cookies means you have to start a lot of thing from scratch and some pages may take longer to load. Once you have extra browsers installed, it is a very simple matter to use a different browser.