Keep loosing the edit buttons with 3.0

Anyone have any idea of why I am loosing the edit buttons for the pages and posts when I update a 14 month old church revolution WP. I have never had the problem before when I updated and backed up, but it is now for the second time doing the same thing. If I click the pages or post, I am getting the following:

“HTTP – 500 Internal Server Error
The page you are attempting to load returned an error.”

I reinstalled my last saved wp and the buttons are back a couple weeks ago, but the update to 3.0 reappears to upgrade again. This is been going on for a month. It is just a circle of upgrade and reinstall and reuse the last WP. It apparently is being caused from some type of internal error as it reads when I click the page or post button.

americas corvette I have about 115 pages now but can’t edit them again.

Thanks for any assistance. I was told to reinstall. That does not seem to work after 4 attempts.