updating to Allegro 5 is pretty much of a hassle, because the backward compatibility is poor, which means month over month over month of new testing...and our programmer just tested the allegro 5 demo programs so far, so there is no guarantee that it will fix the problem with our application.
And there is no general problem with Allegro 4, is there? It works flawlessly in dual monitor mode and all the other intel chipset graphics solutions work flawlessly, too.
The issue is related to allegro 4 (maybe only to Allegro 4).
But it's also related to the HD2000/3000 graphics and its drivers, because we don't encounter such problems with any other graphics solution.