The local storage facility exposed to QML has a bug; if you attempt to open a versioned connection, the version is wrong, and you try to handle that error, the connection is still stored in a connection pool, but in an unopened state. The next time you attempt to connect, no matter if you have the version right or not, the database handle will complain about being unopened.

A patch can be found in these two repositories (I found it impossible to create a merge request against Qt on Gitorious):

https://qt.gitorious.org/qt/hoelzros-qtdeclarative
https://qt.gitorious.org/qt/hoelzros-qtquick1

See also: http://qt-project.org/forums/viewthread/38458/