Long time no post! I saw the new version of Vegas is coming out, and it may be too late but I'm hoping for a response from the new team. It was suggested I start a new thread in that spirit. This happens in Vegas 13 and 14 (not sure about previous versions-it does not happen in Vegas 8 64 bit or 32 or even Vegas 10 for all its other problem).
Eventually while you are deep into a project the project file will hang on opening. The task manager will hit 25% and just stay there. Sometimes you can wait it out. The best solution is to move the project file to a different location, disconnect the hard drive (or change the drive letter), open the file, leave the media offline, reconnect and Vegas will find the media no problem. Edit away.
From there you can delete a file from the timeline, one by one, and you have to also clear it from the Project Media. Keep saving and reopening. Eventually you will find the problem file. Re render it and replace and you can keep going. I have found that the problem file will work perfectly well in other projects, and will not be the culprit.
Some other notes:
1. Turning off waveforms or video thumbnails makes no difference.
2. GPU off or on does not matter.
3. Type of file is inconstant. AVCHD, ProRes, AVI, MP4. Wav *seems* to be the most problematic but not always. It can also happen with a mix of content, or constant content (happened with all AVCHD one time).
4. At least 4 different computers for me. However, never used Vegas on a Mac.
5. Happens with internal and a variety of external drives.
6. Size of project doesn't seem to matter. Can happen quickly with just a few files, or when you are deep in. If you're deep in its a huge time suck to find that one file that is messing up.
7. Nesting doesn't have an effect.
8. Complexity of FX, or plugins, or external (soundforge, boris, hitfilm etc) doesn't matter (can happen on a simple project too).
9. Media Manager (not to be confused with Project Media) is not even installed on my current machine.
It really seems to be just the way the Project Media is loading files on startup. Its a real pain in the but! Just putting this here for the record and hoping that its fixed in Vegas 15!