Many people have had problems with mobile channels. In an effort to correct the errors that they have seen they delete the channels from their devices. They then discover that they can not re-subscribe the channels.
If you choose to delete and resubscribe to the same channel, Mobile Channels does not properly clean up the channel until you subscribe to another mobile channel first.
The recommended way to test content updates is to right-click the mobile channel in the Channel Bar in Internet Explorer 4.0 and choose Update Now. If you must delete and resubscribe to your mobile channel, subscribe to a different mobile channel first, thus forcing Mobile Channels to perform cleanup. Resubscribing to your original mobile channel then initiates the expected download sequence.