I just installed Zenphoto because I need to upload at least 2.000 images to my server for my costumers.

Normally I have to do it one by one, so Zenphoto is a great solution.

I got Zenphoto to work and I activated the ''upload plugin'' so I can upload files (Which is very weird it's not a default setting to start of with).

When I upload Images they are not visible in my album. But when I ''Select everything ctrl+A a tiny clickable pixel appears.

Images of problem:
http://aprilia125.com/shit/zenpotodoesntwork.html

Must I activate yet another Plugin ?

Refreshing database and Meta and the page itself didnt make a difference.

I got Zenphoto to work and I activated the ''upload plugin'' so I can upload files (Which is very weird it's not a default setting to start of with).

It should, this is a bug in the 1.4.5.9 release and is corrected for the 1.4.6 beta already.

As to your problems please followe hte guide for bug reports:
http://www.zenphoto.org/news/general-contributor-guidelines#reporting-bugs
Otherwise we are wild guessing. It could also be that the images and/or the albums are simply not published yet. There is a plugin named publishContent to manage a higher number of items instead of visiting the edit pages.

Or a server overload with the task of 2000 at the time (you might try FTP for that number, too).
Also please read here:
http://www.zenphoto.org/news/problems-with-albums-and-images
As you see just guessing without a proper report.