@etardwebcam: Whatever is happening on your site, it's not something we've seen before. From what I can tell your thumbs are not loading on the album page, and when you click through to galleries, there's a 404. So there appears to be a disconnect between the paths/URLs loading on your site and where the images/files actually live.
Is there anything unique or customized about your NextGEN set up? Anything you've done with how and where images are stored, or any notable customizations?
I'd also run through a couple standard troubleshooting steps - in particular, if you could please try momentarily deactivating other plugin just long enough to see if things work, we could see if there's a plugin conflict.
Otherwise, I might suggest two things:
1) To get you working again now, just roll back to 1.9.13: http://www.nextgen-gallery.com/how-to-rollback-a-version/
2) Then submit a bug report with the details of what happened and login credentials and permission to upgrade you again. Our developers will basically go ahead and upgrade you when they're ready to work on it and immediately resolve the problem, or if it's going to take a while, roll you back again.
That way, you can get working completely right now, and also know that we're going to identify and resolve what's going on with the 2.0 update on your site so you can continue to take advantages of subsequent updates.