Endnote error message when clicking on cite while

I have tried to solve the following user’s problem.  Every time he clicks on  “cite while you write” in Endnote 4 ( Word 2007 ) and types in a few letters of the reference, he gets an endnote error message. 

Looked in disabled in the Add-ins in Word and re-enabled CWYW options but still get the same problem.

Even when he tires to enter a reference on a blank document

Please could someone help me with this.

Assuming you mean X4.  Was there ever an older version of endnote installed on the machine?  sometimes the old version is imcompletely removed and the hooks to the old program are trying to be used?  Have you tried uninstalling all versions of Endnote (as the user) and reinstalling and updating to X4.0.2? Or running the configure endnote (usually available from the start  bar> Endnote dropdown options).