Arduino + Ethernet Shield + Libelium GSM Shield

Hello to all, I'm trying to make a project where i send commands via ethernet and then the arduino sends SMS messages accordingly. I've managed to interface the Arduino + Libelium GSM Shield

When i connect the Ethernet shield also the Heat Regulator on the Arduino gets really hot when i touch it (can not keep finger on) and it does not work. I use a 12V / 2A power supply that works fine for the Libelium + Arduino Duemilanove.

Any ideas on this ?

Thanks a lot, Bye!

Does the regulator get hot with just the ethernet shield attached?

yes. the only time it gets hot is when i attach the ethernet shield. when i use it with the energy junkie GSM shield it works like a charm, but when connecting the Ethernet Shield... all goes hot