Given this set of circumstances (some higher in MB and some lower), the most logical explanation I can think of is that Last's API is sending incorrect data. Open the dat file and search for "Is Everybody Going Crazy?" and see how many times it's in there. If it's more than 10, are there differences in other data (album name for example) in the addded ones.
I know that, if you listen to several different versions of songs with the same title, Last lumps them all together in your stats on the web site. If you look at the scrobbles for that song are 50 of them from albums other than the one represented there in your MB library?