Problems with img_assist during 5.10 to 6.5 upgrade

Everything else went smoothly, but I have a couple of problems with img_assist:

1. The img_assist tokens ([img_assist etc.]) that I was using no longer display images. In fact, they display nothing.
2. The img_assist popup gallery (for selecting images to include) doesn't display any images. It displays page numbers, so it's finding something, but it doesn't display images.

Any suggestions for how I can fix this?

I'm using the image and img_assist modules to handle inline images in pages. I find that Drupal's image handling has always been weak. Is there something more reliable/less fragile available in drupal 6.x?