Internal Server Error When Updating EasyDiscuss

I'm getting an "Internal Server Error" every time I try to update EasyDiscuss from version 3.2.9599 to 3.2.9676 (see attachment) on my Joomla site. I have tried installing by uploading ZIP file and installing from directory with the same result.

Also, EasyDiscuss is no longer listed on the Joomla components menu, but my Forum still looks Ok on the front end. I can see that certain front end features like "Board Statistics" get enabled even though the update does not complete. When I reinstall the old version, I get the same error, but "Board Statistics" goes away from the front end.

Any ideas? My forum is going live in a couple of weeks so I really need to sort this out .