[AccessD] Form Filtering not working

Hi Listers
I'm having a weird problem with one of my forms.

When filtering the form, the filter works the first time ie: it goes to the
correct record.
But the second and subsequent times it remains at the record that was
filtered the first
time.

I know the code that I use to filter the record is 100% correct as the app
has been used
for the last 5 years and this code hasn't been changed.

Has anybody come across anything like this before ?

I have tried removing the filter from the form then applying the new filter
criteria in code
but this has the same result as above ie: works the first time but not the
second and
subsequent times.

Any help appreciated

Cheers Tracy