Hi,
*) if you want to generate the findbugs report via the site plugin, the
configuration should go into the reporting, not build section of the pom
*) AFAICS neither formats nor canGenerate are listed as supported
configuration options of the findbugs plugin:
This is a plugin developed by the Codehaus mojo team[1], not by the Maven team.
So their mailinglist[2] would be a better place to ask this question.
Executing Maven with an additional -X will give you debug-logs, which might
show the problem.
The code you're hitting is [3]. Do you have .class