Whenever I try to Save an edit to the Frontpage featured article at http://blissberry.com I get a Server Error:
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator at webmaster@blissberry.com to inform them of the time this error occurred, and the actions you performed just before this error.
More information about this error may be available in the server error log.
Additionally, a 500 Internal Server Error error was encountered while trying to use an ErrorDocument to handle the request.

I even tried recreating the article, unpublished, under another title, and it wouldn't save it. I tried building it bit by bit and it would Save it up to a certain point, which varied from effort to effort, and then start giving the Server Error.

I found two Warnings in the Extension Manager section: The PHP temporary folder is not set; PHP Upload Size bigger than POST size.

All the other articles on the site are working just fine. This issue has popped up since July 14th when the frontpage was last successfully updated and has been ongoing several weeks now. I'm in over my head on this one so any suggestions would be greatly appreciated.