If a fix works then don't accept anything else. If you write to Sony with a fault, rather than on the Forums, you will get a specific reply, but it can take time..... Yet you seem to have resolved the issue - it's possible your drivers may need updating (Don't we always read that?), but you may just have to render the old-fashioned way . . . . at least until Graphics cards are standardised and can be tested. It would seem to me that a simple Test Graphics button ( or standalone prog?), would be a useful way of sorting out this issue.
The cards that I can buy don't appear to match those that Sony specifies . . . I find it just too difficult to fathom, being a fairly simple fella.