One of the things I do occasionally is make maps and similar drawings, and not infrequently these have to be saved as a bitmap ﬁle, although I create them as vectors. One of the irritating things about Illustrator is its poor handling of large pixel images, even on export, and so the largest vector plots I do (32k points square) won’t render.
In this case, I import the .ai ﬁle into Paintshop, which renders it quite happily.
You can in fact import both .ai and .pdf ﬁles directly into Ps – just “Open” them and youre presented with a dialog with a page selector, colour space, resolution and more. It’s quicker than Illustrator, too!