Missing font on data grid text entry

hello all,
having a really frustrating problem.
I have a file, originally penned by anoother developer in CS3 and resaved as CS4. It uses datagrids extensively. When clicking on a cell in a data grid it now fails to render the font (or a blinking carat for that matter).
When you click off and finish the edit the text you enter is there, of course that isn’t much use because you can’t see what you’re typing.
I haven’t changed how these grids work in anyway, and it was working in CS4 before mysteriously stopping.

Have tried setting the font to one that is embedded in the setStyle of the custom renderer the cell is using but it makes no difference - everything renders fine when not editing but disappears when editing.
Any ideas folks?


roll on CS5