I was using the following charger, but I couldn't get my Raspberry Pi to connect over Ethernet (ethernet lights showed no link): http://www.amazon.com/gp/product/B0038HYPZS
The charger was definitely the problem. I swapped it with a Motorola OEM charger and the Ethernet started working again. I did some quick googling, and haven't seen many reports of this issue yet. I have the Model B, Rev 2.0 board with 512MB RAM.