Problem unenlisting send ****ts.

I've written a vbscript based on the examples provided with BizTalk
to unenlist the send ****ts. When it calls the UnEnlist() method I
always get this error, "Provider is not capable of the attempted
operation  (HRESULT: 80041024)".
   I've also tried checking the status property, of the ****t to see if
it is already unenlisted, but I always get 3 returned. (which from the
help means it's started, but when I look in the BizTalk Admin Console,
it's only stopped)

   Does anyone know how I can get either of these to work? Does the
UnEnlist() method need to be run under a specific user? All of the
other methods run fine under my current user context. (local admin)



Thanks,
Anthony