Speaker docks and iPhone charging?

[vasu]

I have a Directed Soloist (Combo iPod/Sirius speaker dock). It charges my ipods and sirius tuners just fine, but the iphone's a bit different. When I plop the iphone into it, the screen comes up that shows it charging, and the battery icon changes to the charging icon, but it doesn't actually charge. I just noticed that I've had mine docked all day and the battery meter has been dropping instead of holding steady at full.

Has anyone else noticed this? Do all ipod docks do this, or is it a Soloist unique issue perhaps?

-vasu