Command overview does not start because XML does not start

My questions are not directly related to Flexsim, but I searched the InterNet and did not find a solution. Maybe one of you can help me or give me a hint.
If I click in the help menu on Commands the MS Internet Explorer opens, but it is a white page and nothing happens.
I tried directly to open the commands overview (\program\config) usercomands.xml but than the Explorer has as address http:/// and says in German something like that the page can not be shown. I tried different things, but did not get it working.
If I open a *.htm file e.g. commandindex.htm this is working. Also the Explorer itself works, so I can reach the Community Forum.
Any help or hint is appreciated. Thanks in advance.