This is an interesting problem with the iPhone. If you have an Official Apple iPhone, with the Official Apple Sync cable that comes with it and connect it to a PC and Sync within iTunes, the iPhone is both able to synchronise and be charged at the same time.
Now bring into the equation the Official Apple Desktop Charger stand and plug the same Official Apple Sync cable into this and plug the iPhone into it, then Sync through iTunes on the PC and now you receive the message “Charging is not supported with this accessory”
Seeing that there really isn’t anything else the charging stand will do for the iPhone other than Charge and Sync, you would think that the Charging stand/dock would still be able to support both.
If you plug the charging/sync cable into a mains adapter then it will charge the iPhone through that. The iPhone is obviously capable of both Charging and Syncing to a PC because it can do that via the cable directly, just not when you bring the iPhone desktop stand into the equation.
The woes of technology and accessories. This is the main reason why I usually purchase ‘Official’ accessories as you can understand why some third party clone accessory won’t work or will for a time then stop working, but you really don’t expect this from Apple seeing that they made the stand and the iPhone. 
Respectfully disagreed with “always buy official accessories”. Mines came with brand new 3Gs, and still got the above mentioned issue, not charging while sync with the same message alas!
By: Didithu on June 2, 2010
at 6:07 am