When you connect it says "connected at 28kb/s"?
Could be bad wireing, range issue, driver issue, modem hardware issue, and more. I'd say try another phone jack, reinstall the modem, try a different modem if possible. Or better yet have a friend bring over their comp and make the connection on their comp.
If all of the above don't solve the problem it is pretty much narrowed down to a wireing or distance problem.