I finally bit the bullet and updated to Vegas Pro 17 build 421. Updated the latest versions of Effects and Image, de-registered and re-registered Vegas 17 as advised in the Post release notes. Attempted to edit a media event in Vegas Effects, Effects launched into the UI then closed down and the error as shown appeared.

Attempted to edit another media event in Effects (the original one on the timeline was now a .vegfx file), the Effects UI opened then closed with the following error.

Has anyone had any luck updating Post? I can't see were I'm going wrong.