Can't save/convert videos or images even using Media Converter

I bought a Sansa e250, upgraded its firmware and downloaded the latest (86MB!) Media Converter from Sansa's website.

Following all the directions, I've tried converting videos and images (JPGs). All the files are converted and saved to the appropriate folders on the Sansa. I can open and view the files on my PC.
However, the Sansa doesn't recognize them. Specifically:

1. Despite converting a handful of images only one new blank(!) image shows in the Photos/Thumbnail folder. If I click on it, it tells me "use Media Converter" to convert this file. (I just did).
2. No new videos show in the video folder at all.

I'm bothered by the fact that all the demo images are BMP files (which don't load in my image editor). Yet, Media Converter is saving JPGs.

I also wonder if you can only add JPGs and videos to an SD card. I'm trying to load files to the 2G base memory.

Anyone know any tricks for adding images and videos to the Sansa?