Palladin--
Another possibility...I'm sure you know if you use your reader to listen to audiobooks/mp3 files, it will drain the battery fairly quickly. I've read about some people who have problems with their 505 and audio files. It seems that sometimes it can be easy to not actually turn the audio player off. If this is the case, then that's what could be draining the battery on your 700. I highly recommend buying a cheap mp3 player for listening to audio files and not trying to use your reader for that.
dordale