Operation not supported in transactions

Hi,

I have a form with a subform, the user can select a supplier from the
main form and the sub form will display all related products for this
supplier.

If the user then does a find and replace on say the discount column
and does a global change i.e. changes all fields that contain 10% to
0% then this would appear to break the connection between the subform
and the mainform and more importantly actually doesn't change
anything.

This only becomes apparent if you attempt to refresh the subform by
using F5 when you get the error 'Operation not supported in
transactions'. At this point clicking OK shows all the related fields
as #deleted#.

Question is:

1) Why does this happen?
2) Is there a work around?
3) If the use of find and replace is not a good idea how can I switch
it off?
4) Are there any other scenarios that would cause the same problem?

Thanks