What's causing the Sirius XM app to stutter even with a good 3G signal or WiFi connection?

More often than not, the Sirius XM app has trouble streaming content when the screen turns off - it will replay the same buffered audio in a loop (usually 20 or 30 seconds worth) until I turn the screen on and unlock the screen.

This happens even when using WiFi - when going 8 feet to my PC (where the wireless router is) and logging into the XM Radio Online site, there are no problems streaming content.

Is there a way to give network priority to an app when the screen is off? Is this a common problem with other apps?

I have an HTC Droid Incredible (with the 2.2 update).