There are a couple of articles on the Horizon/Spektrum sites that talk about power requirements for the AR7000 receiver. Battery capacity IS critical with the DX7 receivers. A 900mah 4.8v battery may not be enough for digital servos depending on the load. Under high loads, if the voltage drops below 3.5v, the receiver will re-boot, giving the symptoms you described. I'm not saying that is for sure what happened, but I would do the tests in the first article to be sure.

[link=http://www.spektrumrc.com/Articles/Article.aspx?ArticleID=1683]First article[/link]
[link=http://www.horizonhobby.com/Articles/Article.aspx?ArticleID=1674]Second article[/link]

I hope this helps.

Bob