Iphone 4 not charging after update to iOS6
The phone will charge even when the OS is powered down. Why not plug in your device and power it off (or wait for the battery to die and plug it in) and see.

If it won't charge after an OS update, you can be sure that there is a hardware issue with the charging circuitry. It's possible for a phone to get stuck in a loop where the CPU can take more power than a charger can provide, so the power cycle (or inevitable loss of battery power) could be needed to clear things and let it take a charge.