Well, I created 3 PNGS, all of them according to your spec(22″ x 9″ @300)
1. Using File > Export (PNG). This does not allow to specify exporting alpha channels (grayed out).
2. Using File > Save for Web. I saved the file as transparent 8bit PNG.
3. Using File > Save for Web. I saved the file as transparent 24bit PNG.
In all cases illustrator imported the linked files without any problems.
WinXP Pro SP3 | 4G | 32bit
CS4