Hmm, seems many people have problems with their H264 encoded videos, and so I have decided to help you by creating this cab file. Copy it onto your device and install it. It consists two codecs - AVC and AAC, both are very good - I can watch H246 movies even with my CPU set to 208MHz. I hope this will help you.
Here's the cab file I created. =>
http://www.box.net/public/gk97uv7x1o
Yours sincerely,
Vulpix
(I suggest you to use cabinstl.exe - that way you can specify the installation directory => download here
http://www.freewareppc.com/utilities/cabinstl.shtml )