I noticed the same behaviour with the latest Beta3.
When I try to create the statistics report with my converted library (~70K tracks) MMB3 seems to hang. In task manager I can see that the memory usage changes and increases over time. I let it hang for more than 5 hours before killing and it was showing a memory usage of more than 120 MByte.
So, I started with an empty data base and just imported about a hundred tracks. When I tried to create the statistics report I got exactly the same errors as "gege".
I'm not sure if the statistics report is supposed to work in the current Beta3.
I posted a question to clarify this to the developers in another thread but didn't get an answer yet.