I’d take a long, hard look at which municipal bonds are contained within any fund, seriously. Jefferson County, Alabama is something to look at. Bond insurers themselves have not been immune to financial stress due to mortgage-related securities. Syncora Guarantee Inc. and Financial Guaranty Insurance Co., two of the major bond insurors, had their credit ratings reduced in 2008. Bloomberg has an informative article on this, I’d post an excerpt but I believe this is not permitted. It should come up easily on a search engine.