Thread tries to read from or write to virtual address python QtSql

Question

I have two issues - first off (and more importantly) the second time the code is run from the QGIS Python it fails with "The thread tried to read from or write to a virtual address for which it does not have the appropriate access".

The second issue is that if I close and remove the database the table displayed using projectView.show() is empty yet if I comment those lines out, the data displays correctly.

from PyQt4.QtSql import *
from PyQt4.QtGui import *
from qgis.gui import *

db = QSqlDatabase.addDatabase('QODBC')
if db.isValid():
   db.setDatabaseName('DRIVER={SQL Server};SERVER=%s;DATABASE=%s;UID=%s;PWD=%s;'
                    % ('ServerName',
                      'Database',
                       'username',
                       'password'))   

    #print "db.isValid"

    if db.open():
        #print "success"
        query = db.exec_("""SELECT TOP 100 postal_address as address, EASTING as x, NORTHING as y FROM dbo.POSTAL_ADDRESS WHERE postal_address LIKE('%EX3 %')""")

        projectModel = QSqlQueryModel()
        projectModel.setQuery(query)
        projectView = QTableView()
        projectView.setModel(projectModel)

        projectView.show()    

        QMessageBox.warning(None, "Info", "hello")

        query = db.exec_("""SELECT TOP 100 postal_address as address, EASTING as x, NORTHING as y FROM dbo.POSTAL_ADDRESS WHERE postal_address LIKE('%EX2 %')""")

        projectModel = QSqlQueryModel()
        projectModel.setQuery(query)
        projectView = QTableView()
        projectView.setModel(projectModel)

        projectView.show()    

        #db.close()
        #db.removeDatabase('QODBC')       

    else:
        QMessageBox.warning(None, "Info", "Error")
 else:
    QMessageBox.warning(None, "Info", "Error")