Room Acoustics Problem????

I'm hoping someone can provide some input to resolve what I "think" is a room acoustics problem. I have a HT setup in a rectangular shaped room approximately 20' (L) by 12' (W). My television and front speakers are located on the length of the room. Although I have 5 speakers in the room for surround HT sound, I listen a great deal to 2 channel as well. What I'm noticing is that the left speaker always appears to be louder than the right speaker, throwing the sound off-balance. After reading a few articles on room acoustics, I'm attributing the louder sound to the bay windows which are located next to the left speaker. I'm assuming the bay windows add increased reflections in the sound. The right speaker is located next to an open space so there is no added reflections from that speaker.

Is there an easy way of fixing this problem other than using the balance control to change the output? Would adding absorption materials near the bay windows (maybe curtains?) solve the problem? I'm hoping that I could come up with a simple solution without spending too much money. Any advice would be appreciated!

Tony