FRZMAO-
I didn't look TOO hard online but what I did see (on several sites) were commensurate with your numbers.  Poking around further all I could find was how easy it is to do election-day registration in MN.  Something doesn't compute, however, because with about 1.8 million votes in this last election why would there be about 500k voters registering nearly every four years?  Doesn't make sense even if you account for those changing party affiliation.  However, having said all of that, there is no evidence of voter fraud that I've turned up.  
To me the biggest problem in terms of voting "fraud" is the deliberate attempts at disenfranchisement by the GOP.  Like how Texas requires an ID - which to me is fine in and of itself if the ID is easy for ALL to obtain - but then they'll accept gun licenses but not school ID's.  Gee, can you be any more transparent about who you are trying to serve?  That, to me, is disgusting and should be illegal...