I bought my RPi board from element14 including a case later on with heat sinks. They seem to sell good stuff (when it comes from UK to my country anyway).
Perhaps you could try contacting them regarding getting it fixed?
Have you tried getting a mobile charger that gives more power to your board (while following the required voltage and current values)?
RPi boards are not known to give any issues unless they're:
2. Have OS issues
1. Changing the power charger/power socket where you connect the charger - Mobile chargers that are made for high end smart-phones work very well.
2. Burning a new image onto your SD card with an official OS from the RPi site.
3. If both don't work, try contacting element14.
If all else fails, write to Eben Upton (co-founder of RPi). He lives in UK ;)