Morten,
It has been a while since I last used a UFL with Crystal or Logicity but I am fairly certain they work just fine so long as you place the DLL in the folder:
C:\Program Files (x86)\SAP BusinessObjects\Crystal Reports for .NET Framework 4.0\Common\SAP BusinessObjects Enterprise XI 4.0\win32_x86
Give that a shot and let us know if it seems to work correctly for you,
Adam