Rewrite module weirdness

I've seen that a couple of other people have had the same problem, no one had an answer.

I've installed the URL rewrite module, 75% of the time it doesn't show up under the admin page. When it does, if I click on it, it asks me to log in and says my session has expired. The message continues even when I re-enter my details.

This is on DreamHost if it helps.

Thanks,
Doug