The HDBC-mysql package is currently broken for me. The fix is in this fork. How can I specify that I want cabal to build from this fork of HDBC-mysql?
If you just want to get stuff up and running, just checkout and build manually.
> git clone https://github.com/markus7/hdbc-mysql.git
> cd hdbc-mysql
> cabal install
This should keep things working until the new changes have been pushed to Hackage.
(note- It is possible that you will have to fiddle with dependencies to get the project to use this version.... But I would just try the simple install first and see if it works).