MitkWorkbench's error message:

Exception occured when reading file /home/mhettich/LPS_12x12x12_111-11001-1_klar.nrrd:
/home/mhettich/MITKsuperbitch/ep/src/ITK/Modules/IO/NRRD/src/itkNrrdImageIO.cxx:756:
itk::ERROR: NrrdImageIO(0x452e820): Read: Error reading /home/mhettich/LPS_12x12x12_111-11001-1_klar.nrrd:
[nrrd] nrrdLoad: trouble reading "/home/mhettich/LPS_12x12x12_111-11001-1_klar.nrrd"
[nrrd] nrrdRead: trouble
[nrrd] _nrrdRead: trouble reading NRRD file
[nrrd] _nrrdFormatNRRD_read:
[nrrd] _nrrdEncodingAscii_read: couldn't parse element 1 of 1728 ("#")

http://teem.sourceforge.net/nrrd/format.html says:

Comment lines start with a pound, "#", with no proceeding whitespace.
The comment string itself starts with the first character which is a not a pound or a space (" ").
Comment lines with a zero-length comment string should be ignored.
Comment lines may be interspersed with field specifications in any order.
This allows field specifications to be commented out and commented upon easily.
Gracious NRRD readers should store all the comments seen in the header, but this is not a requirement.
Comments are case sensitive.