You may try to open the <avast>\data\avast4.ini file and in the [Common] section, change the item Database=ODBC to Database=XML. This could prevent the Microsoft Jet drivers from accessing the database... does it have any (positive) effect?
If you ask which is better ODBC or XML? I'll say that for the Home version, they are equal. For the Professional version of avast!, XML is missing some functionality (compared to ODBC).