Vinnie,
I have never experienced a problem like this with any of my receivers. As far as customer service goes, Denon should definately accomodate you in some way.
I am not clear on the warranty of a Denon receiver. My Marantz is for 3 years. Although your product may be under warranty and only covers return shipping, parts and labor; I would strongly recommend calling them back and complaining that it should not cost you over $100 to ship to them everytime. Especially if the first repair did not fix the original problem.
The problem that you are experiencing is not in any way normal. Are you using a surge protector? In my opinion, they should at the very lease offer you a pre-paid airbill (shipping label) for you to use in sending your receiver back for re-repair. Maybe a factory refurbished receiver as a last resort?
Good Luck
JC
