When I save a grid (updateable grid, DBF), I'm getting a blank overlay, seems to be an error window, but I can't tell. It flashes by quickly most of the time, does not happen all the time. It happens during the save process, which usually takes a few seconds (large file, lots of fields)

Nothing complicated or unusual in the grid, nothing but the standard selections, no calculations, javascript or anything other than simple fields in a form.

Screenshot attached.

Anyone else come across this?