Gerard,
I never use 'set filter'. The behaviour you hit is one of the reasons for I never use it - before I posted a code portion similarly showing weird results with set filter when expression was a dynamically changing one (date in that case, near midnight).
However if I ever would do I would keep the expression variables in scope (maybe oApp.MyTable.MyFilter or alike) or set literal values rather than references.
Cetin

>Cetin, I think I have got to the bottom of it
>I did have a filter on the file (set filter to cusref = thisform.objMemvar.Cusref) which is set in the calling screen.
>
>In the called screen,presumably this filter is still on but it cannot find ThisForm.. now because the ThisForm is now the calling Parent.
>
>(Maybe the reason it did not error out on a Seek 'abc' was because the seek got an EOF and it did not trigger the filter ??
>
>Anyway, this poses another problem. Is there a way of maintaining a filter across called screens (I have set up called screens so they share the DE)
>
>regards,
>
>Gerard
>