Error Message after Trying to Edit

I tried to insert a new image in a post, when I tried to preview it I got this message.

"Your browser sent a request that this server could not understand. Additionally, a 403 Forbidden error was encountered while trying to use an ErrorDocument to handle the request."

I am not sure if I had this problem before I tried to do the edits, but both pages I tried to makes these edits to have directed me to this error page.

Here are the links:
http://norcalrunning.com/2011/02/20/...nning-with-man
http://norcalrunning.com/2011/02/20/...ad-of-options/


You can see that the first half of the posts work: http://norcalrunning.com/2011/02/20/
It is just the "More" pages that don't work.

Any ideas?

Thanks!