This is really wierd that I got a call from my bike mechanic saying that the American Classic rear hub on my Mu SL is not a Shimano compatible hub and will not take a standard Shimano 9 speed cassette. They tried fitting Shimano, SRAM and SunRace cassettes but the splines don't match in any combination. Is this unique to the 2007 Dahon Mu SL model and how do I get the new cassette to fit?

Thanks!