I was getting the following .NET error. It vanished when I put my project on a local drive rather than a network drive:

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NotSupportedException
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Exception:
The given path's format is not supported.

Stack trace:
at System.Security.Util.StringExpressionSet.CanonicalizePath(String path, Boolean needFullPath)
at System.Security.Util.StringExpressionSet.AddExpressions(String[] str, Boolean checkForDuplicates, Boolean needFullPath)
at System.Security.Permissions.FileIOPermission.AddPathList(FileIOPermissionAccess access, String[] pathListOrig, Boolean checkForDuplicates, Boolean needFullPath, Boolean copyPathList)
at System.Security.Permissions.FileIOPermission..ctor(FileIOPermissionAccess access, String[] pathList, Boolean checkForDuplicates, Boolean needFullPath)
at System.IO.FileInfo..ctor(String fileName)
at ComponentCategoryRegistrar.esriSamples.AddInUtilities.AddInUtilities.create_txt_file(String fn)
at ComponentCategoryRegistrar.Reflect_mod.write_reg_file()
at ComponentCategoryRegistrar.Reflect_mod.write_cat()
at ComponentCategoryRegistrar.Connect.Exec(String cmdName, vsCommandExecOption executeOption, Object& varIn, Object& varOut, Boolean& handled)
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OK
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