I think that msn is penalizing domains with more than one dash. This is anecdotal, but look at these highly spammed terms:
Viagra, #4 & #10, one dash.
Home Mortgage, #10
Free Porn, #1 & #5
Diet Pills, #1, #2, #4, #8
MSN used to be hammered with domains with tons of dashes in them. I suspect they just programmed a rule that gave some very negative weight to domains, or even URLs with multiple dashes in them. Because of this I don't touch dash domains anymore. Granted, if you are doing anything more than spamming you shouldn't have them anyways.