William-

PMFJI, I'd urge you to not resort to ON ERROR *, which is brutish and can mask legitimate errors with devastating results. If you can't resolve the error itself using Sergey's FAQ, then I would suggest trapping the error in the combo's error method. So, for example,

* Combo.Error()
Procedure Error
Lparameters nError, cMethod, nLine
If nError = 1152 && "Cannot access the selected table ".
  * We are just eating this error for now because it doesn't seem to be doing any harm.
  * However, we still need to find the cause!
Else
  if version(2)=2
    Assert .F. Message Message() && Give programmer a chance to debug any errors
  else
    Local lni
    lni = Messagebox(Message(),2+16+512,"Error in date field")
    Do Case
    Case lni = 3 && Abort
      Cancel
    Case lni = 4 && Retry
      Retry
    Case lni = 5 && Ignore
      Return
    Endcase
  Endif
Endif
Endproc

BTW, a neat little trick: if you do break the program, set the next program statement to the RETY line and step. You'll then have a chance to see what code was generating the error. Unless the problem is coming because of a property setting, as Sergey's FAQ mentions.

Good luck with finding the solution. I, too, almost always work on inherited code, and it has its own special challenges.