Compatability Issue or Not? Grado Sonata and MMF 7

I have a MMF-7 Turntable and I am thinking of buying a Grado Sonata cartridge. Currently I am using a Blue Point cartridge. I read somewhere where my turntable is susceptable to hum with this cartridge, like the Rega's are. When I mentioned this to the store which is trying to sell it, they said, "as long as you ground it, it will not hum". (I ground the MMF-7 to the back of my VITB phono amp)
However, because it is a cartridge I can not return it(I would hate to have buy a cartridge twice!). It is also used. I would like to know if anyone has any experience using the Grado Reference line with a MMF turntable.

Thanx in advance for your help, I really appreciate it!
If they haven't changed much since the late 80's I'd guess that the issue with some of the Grado cartridges is shielding, and NOT grounding. The Grado cartridges back then were unshielded by choice...I forget the logic, but seem to recall that Joe Grado had some reason for doing so. I had (and still have, though not in use) the original AR Turntable from the mid-80's, and it had the same issue with the Grado cartridges. One company, I think it may have been Merril, even marketed a lead 'shield' that mounted between the arm and plinth to shield the cartridge from the motor. It had limited effectiveness. I had both a Blue Point Special, as well as a Grado Signature (don't know which, but it was their $600 model in the mid-80's). The Blue Point was a bargain and not a bad cartridge at all, but the Grado was really wonderful, warm and detailed as I recall. The hum was a small price to pay for the bang-for-the-buck! Don't know how bad it may, or may not be on the MMF-7. If shielding is the issue, grounding won't help. Hope that can assist you figure out the issue.
It is a problem for the Rega's because the moter is beneith the platter and the unsheilded cart would pick this up. With your moter being off to the side I see no problems. Great cart; I have one myself and love it. Mike
Thanks for the infomation. I do appreciate your response. I agree with both of you! I think someone on another post may of made a mistake, or, they were refering to a different mmf.
I think the issue w/ the Rega's is the shielding and with the mmf-7's motor so far from the cartridge I shouldn't have this problem if I go for the Grado. Now, if only I could make up my mind which cartidge to buy!