Most likely your code (as well as the Distribution Monitor sample) are not correctly converting the UInt64 Structure to a valid 64 bit number. Odds are something is getting truncated there.
Take a look at this thread for details on how to correctly convert the 64 bit number (assuming you are using VS.NET). Java, as far as I know doesn't support 64 bit numbers. If anyone knows a solution for supporting 64 bit values in Java, please let me know...
http://devcentral.f5.com/Default.aspx?tabid=53&view=topic&forumid=1&postid=11286
Click here
-Joe
Nimbostratus