I bought four TL-PA211 Mini Powerline Adapters in August 2011. The bad news is that all four have failed as you describe with no lights showing. However, the good news is that TP-Link offer a 3 year warranty on these and all four have now been replaced. Mind you, I have spent enough in postage sending them back to pay for one of them outright!

Curiously, the first three were replaced with TL0PA210 Nano Powerline Adapters which are smaller than the original TL-PA211 Minis. The fourth has just been replaced with a TL-PA211 Nano which leaves me rather confused. They appear to be recycling old model numbers.

Try contacting customer support for a replacement. You should be covered provided that you can prove when you bought them.