This is not guaranteed to work, but is your best shot. I too have had lots of signal issues with 802.11n, some of which are due to older 802.11n draft hardware not properly communicating with new 802.11n hardware; other issues are due to interference with other devices (one customer of mine has a cordless phone system which makes their laptop drop off.)
First thing to try is going into your router and change the channel. You're probably set to either AUTO or Channel 6. Pick something at the far top or bottom of the spectrum. Try both if you find the first one doesn't work.
Another thing which I would suggest is updating the firmware on both the router AND on the wireless card in your laptop. If there is not a firmware update for the laptop, just make sure you have the latest drivers.
How close is your router to your speakers? You probably want your laptop to be in the same room I am sure, but you may need to move the router elsewhere. It may be too powerful to sit right next to your speakers.
Speakers have a tendency to pick up crazy interference. I know many people who's speakers make terrible noises when I simply walk too close and I have my blackberry in my pocket. You could try shielding the speakers or buying speakers that are properly shielded. MOST computer speakers are properly shielded so they don't interfere with CRT monitors, but I still see this problem sometimes.
And like you said, you can always switch back to 802.11g if you did not have those problems before. Unless you are transferring files between systems wirelessly, you will not notice a degradation in speed with 802.11g unless you have an internet connection faster than 54mbits/sec.