The Bengali government's investigation came in response to an investigation by the Norwegian government (which turned up nothing, to be fair): http://www.telegraph.co.uk/finance/newsbysector/banksandfina...
I encourage you to read the article. The bank has become involved in all sorts of unrelated enterprises. And micro lending has hit major snags in India, where it has strayed from the original principles of Grameen and become a general payday scam.
I'm far from one to defend the Bengali government. It's the poster child of a well intentioned democracy that ultimately succumbed to the character flaws of its polity. The trajectory was a bitter disappointment to my dad, who was an enthusiastic college student during the Bengali independence.
All that said, there are two sides to every story, especially in a place like Bangladesh. The comments below are certainly true, though: Dr. Yunus has contemplated getting into politics and that has the existing parties, headed by hereditary chairwoman, very nervous.