It happened to me a few times. My solution was undock the explorer and afterwards uncheck the explorer in the menu View. Close Vegas and restart the PC. After the new start check the explorer again and dock te window. Most of the times now my whole content was visible again.
Thx Corninco for your response! But sadly it doesn't work! What I find strange, is the fact that the problem is given with only 1 of my HDs. I can perfeclty browse the others . ... And it's new... I tried to reinstall and even restore my system to earlier time (like long time ago when I was working fine with vegas ) and nothing!!! It's driving me crazy !!! :)
but anyway I still feel that is a HD problem , because I have really no other explanation... So i will test with a brand new one and keep this terabyte for "funny cat web video " ;-)