Do you have DIRECTV'S newest high-def receiver? The H20? If you do we are confident that it runs hot 'cause most of 'em do. We don't know why (someone can tell us if they know) but we do have a solution for you that we found on AVSForums. Simply, well not super easy but still easy, install a fan on the inside of the unit. We are just talking about a normal 80mm fan that you would use in your computer. If you are going to do this though, make sure you spend the few extra bucks to get a quiet one too; there is nothing worse then a noisy fan mixed in with your AV equipment. You might even want to do a slow 120mm fan as they are historically a bit slower and therefore more quiet.
This would require you to take apart the box and keep in mind that if it was 'purchased' after March 1st, this must void some type of user agreement as you don't own the box but are leasing it. The fan plugs into the USB port on the back panel though and since you aren't touching anything on the board, if you take your time chances are DIRECTV won't even notice your were playing around inside of their equipment.