Thanks! When watching the buildwindow, I realised there was no text in my document. I find it weird that this can cause such problems, but it's solved now . Thank you!
But I think I will switch to another pdf-viewer, to avoid other problems.
I've got a problem with TeXnicCenter. When I click at "Build and view current file", this is what happens:
An error that says the document can't be found appears. Adobe Reader opens, but without a document. A second error appears: [DocOpen("%bm.pdf")][FileOpen("%bm.pdf") Cannot execute ...