Vegas 9.0a some video events are red instead of thumbnail
 

After opening a project today, I noticed many video events are bright red instead of the thumbnails.. I would need to zoom in all the way for the event's thumbnail to be rebuilt. Why is this happening?

it's been my experience that RED = corrupt clip. Now that could be any number of things. One bad frame MIGHT cause it.
I've experienced it on occassion with images I pull from a still camera-the image is so large that Vegas chokes on it and it goes RED but not always.
You might close everything out and reboot then reopen Vegas and try pulling the clip in again. If it doesn't work at least you can take that off the list.

Yang, this has been reported a few times on the Sony Vegas forum and it appears to be yet another 9.0a bug.
Please file a detailed report with Sony Technical Support in the hopes that they will get it fixed sooner rather than later.