Both of these issues are related. It's having trouble loading the available Sony Vegas templates on one of the TandemVids rendering tabs.
On the USB, YouTube, DVD and Blu-ray tabs, note the currently displayed template and then click the default button next to the rendering engines and restart TandemVids. This should fix the error on every start. Now reset the rendering engines to the ones you previously had selected. I'm guessing one of them, maybe a customised one is no longer available.
The YouTube error is slightly different but probably related. It can't find the file to set the meta data so the erroneous rendering engine specified earlier probably failed to produce a valid file ready for upload. Delete the uploads from the YouTube upload application and render them again from TandemVids. You can right click multiple customers on the Search tab in TandemVids and select queue for upload. On the Queue tab, process the queued uploads. This will render and upload the videos.
How you wound up in this situation is a concern. Did you recently change your version of Sony Vegas or move TandemVids to a new computer?
Mick Hardy attached the following image(s):