I have installed and configured Tridion 2013. It is working like a charm now. Then I've installed and configured the Experience Manager without any visible problems. But when I tried to test it on a HelloWorld page, it failed to update the preview with an {"error":"Internal Server error"}
message.
I recorded a short video showing what the problem is and how it happens - http://screencast.com/t/yPKhLLrh.
This error also appears sometimes when I try to just open my HelloWorld page in the browser. It seems that it happens randomly.
I've installed the Experience Manager Web Service following the video provided by the live SDL Tridion 2013 documentation. Yesterday I had no such a problem and I haven't changed anything...
Have anyone of you ever experienced the same problem or at least similar?
Do you have any suggestions/advice?
Thank you in advance and looking forward to your replies.