The question is confusing me a little. When you say Maya runs slow or stops during rendering, are you batch rendering? If so, it could be because the Maya batch is taking too much of your resources, which you may not even have enough of in the first place.

Huh, you can animate in Real Player? Or do you mean, render out an animation to view in Real Player? You might want to take a look at the basic rigging/animation tuts in the help files and Mikes How to Render a Movie video.