[Haskell-cafe] thread blocked indefinitely in an STM transaction

Hi everyone, I'm writing an API server using the snap framework with the new snaplet infrastructure. In order to connect with the database, I'm using snaplet-hdbc, HDBC, HDBC-mysql. (I'm using InnoDB for storage engine so it can process transaction). Every query is wrapped in the function withTransaction' so I don't have to commit or rollback by hand. If there's a SqlError raised, I will catch it, log the error and return an error message to the client side. But when running the program, if there's a DB error, the process will be blocked and there's an error message: " thread blocked indefinitely in an STM transaction". There's no STM related code in my code. Do you have any idea on this error and how to process this? Thanks. Eric.