Thanks Jason! It helped a lot. Dreamweaver works now. But it seems to have been something wrong with certain XTensions.
I have now reinstalled all the extensions (Data Bridge 1.2.1, Free Tools 1.1.2, Design Extender 1.2.0 and 5.0.7 ECART).
Now, when I select 'WebAssist -> Database -> Computer Assist Pages - I get an error message.
Could the problem be that I have reinstalled the extension in the wrong order?