A reinstall won't help but the event settings will be maintained if you do. It's some kind of configuration issue. When the YouTube video renders, where does the file get created?
When it tries to upload, it's looking for the file in the correct place so the file is rendered to a different location or not created at all.
Open an existing customer, tick the YouTube option and process them so the file to upload is rendered. Take note of the filename displayed in the bottom status bar of Vegas during the render and ensure it matches the file being searched for. The last few characters and the extension are the only bits you need to remember. When the error is displayed, press CTRL + C to copy the message text. Paste it into Notepad and then search your computer for the missing filename.
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