Hello,
I saw some threads here about problems people were having with some RTF files and I experienced the same thing last night when working with some of my files.
What I discovered, however, was this: initially I was working with the files in Word, and when transferred they didn't work. So on a hunch I opened the file in TextEdit (on the Mac), made a change, and saved it. The file shrunk from 12MB to 2MB and looked identical. After transferring over the the Reader it opened up and looked great!
I didn't try WordPad but it may be an option for Windows users...
--Alexis