According to Sandy

Mercury goes retrograde in the Earth sign of Capricorn – December 26 until January 15, 2010.  (Previous retrogrades for 2009 all involved Air signs – now it will occur in the stable, business focused, ambitious Capricorn.)

This change from Air to Earth can mean a difference in the area of life where the influence of Mercury’s backward movement can be felt, but regardless, with this planet it is all about communications. So by now you know the drill – review, reconsider what you say, and write – until mid January when Mercury goes forward again.

And:

Mars goes retrograde as of 12/20/09 in the Fire sign of Leo. It will go backwards in the same sign until March 10, 2010 and reverse. – (since this planet only goes backwards every 2 years or so, you have to pay attention when it changes direction.)

Watch for any temper and volatility issues as this “you wanna piece of me?” red planet slows down. Once fully in backward motion, you might notice a stall in certain areas of your life (creativity, career/business, etc) – things were jumping and then all of a sudden not.

Fiery, energetic Mars may not be sparking the plugs as it usually does. You might want to look again at the actions you are planning – any fine tuning, re evaluation needed? This is a good time to do it. Life won’t stop. You may need to prod things along, but events will start to bounce again after early March.