Don't think you can do that yet, you may be able to hook camera up to computer - put photos from computer to the camera, then hook camera up to 622 to add those photos.
Pick up one of those little plug-in memory sticks ($20 at BestBuy). I used a 512 MB SanDisk Cruzer and transfered a bunch of photos from my computer to both my 622 and 942 - it worked gread. My computer's USB is only USB 1 too and it still worked pretty fast, so USB 2 should fly.