Problem with Glossary Converter app.

When I try to drag an xls file into the Glossary Converter app. I get an error message - see the attached files.

Object reference not set to an instance of an object.

Source: GlossaryConverter
   at Sdl.MultiTerm.Tools.GlossaryConverter.Filters.ExcelReader.Initialise(String filePath)
   at Sdl.MultiTerm.Tools.GlossaryConverter.Core.FieldReader.Read(List`1 inputFilters, List`1 inputPaths)
   at Sdl.MultiTerm.Tools.GlossaryConverter.Workflow.Converter.Convert(List`1 inputFilters, List`1 inputPaths, IFilter outputFilter)
   at Sdl.MultiTerm.Tools.GlossaryConverter.Workflow.FileHandler.HandleMultipleFiles(List`1 files)
   at Sdl.MultiTerm.Tools.GlossaryConverter.Workflow.FileHandler.ProcessFiles(List`1 files)

Program version 4.5.6191.34915

Windows version: Windows 7, Build 7601, Service Pack 1, 64 bit (Danish (Denmark))

.net versions:
v1.1.4322    SP0
1033    SP0
v2.0.50727  2.0.50727.5420  SP2
v3.0  3.0.30729.5420  SP2
v3.5  3.5.30729.5420  SP1
Client  4.6.01055
Full  4.6.01055
Client  4.0.0.0

 Excel version: 11.0
 Libre/OpenOffice version: 

 MultiTerm version: MultiTerm 14.0.0.0
BEKO-Terms_121212.xls