Drupal Install w/PEAR ADO module

Has anybody tried installing Drupal 4.3 on Win2K/PHP 4.2.2/MSSQL using the PEAR ADO module to access the DB rather than the mssql functions? My hosting provider disables the php_mssql.dll module and insists that PHP users use ADO COM objects to access databases. I think I've managed to tweak the code enough to get the object classes and functions all playing nicely, only the first time it calls the query function I get an ADODB error that the connection object
$this->connection won't support the Execute(); Method for running SQL queries because the connection object is closed.

Now I've run through a heap of step by step execution and testing, I know that the connection object is DEFINITELY being created and opened. For some reason it seems that it closes the connection again at some point between opening it and executing the query function. This is happening at the very first stage of initialising Drupal - while running index.php, so I don't see why it would be calling DB::disconnect inbetween queries.

Has anybody got any ideas, cos I'm about all out of them!