xDiffPatcher Problem

[Jedzkie]

i always get this problem when diffing

"Exception Source:      xDiffPatcher

Exception Type:        System.NullReferenceException
Exception Message:     Object reference not set to an instance of an object.
Exception Target Site: CheckInput
 
   at xDiffPatcher.DiffInput.CheckInput(String value, DiffInput input)
   at xDiffPatcher.DiffFile.ApplyPatch(DiffPatch patch, Byte[]& buf, BinaryReader r)
   at xDiffPatcher.DiffFile.Patch(String inputFile, String fileName)
   at xDiffPatcher.frmMain.btnSave_Click(Object sender, EventArgs e)
   at System.Windows.Forms.Control.OnClick(EventArgs"
 
Please help!
 
My Client : 2013-03-20eRagexe