Click on the top-left event and then on the bottom-right event while holding the Shift key.
If you are looking for one-click solution, take a look at this tool
Other scripting plug-ins contain similar tools, too.
1) Vegas Pro 10 has Sony AVC renderer (h264) with appropriate templates for Youtube (use Mainconcept AVC renderer in Vegas Pro 11 or newer)
2) Try free Video4YouTube plug-in
3) Read more
This is a well-known (and one of the most annoying) bugs in Vegas Pro. There is no solution, as far as I know, except if you have a backup copy of your project. AutoSave from Excalibur or Backups from Vegasaur can protect you from such problems in the future.
Vegasaur provides the advanced tool for batch rendering – Transcoder that will process your files with ease. Also there is the Markers tool, which can help you to create regions with original file names.