I had the same issue, but on Windows 8 Release Preview. It seems the fiber package shipped with Meteor 0.3.7 is not working properly. Here is what worked for me:
First, I opened a command prompt with administrator privileges and went to:
C:\Program Files\Meteor\lib
Or in your case:
C:\Programme\Meteor\lib
And then just reinstall the fibers:
npm remove fibers npm install fibers
Let me know if this works for you.
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