Weird Behavior on connecting

[Tom Davey]

Hello,
Using a simple, barebones .NET 2.0 application (C#), I am trying to connect
to a simple encrypted Access 2007 database in the same directory, like so...

oleMyDbConnection = new System.Data.OleDb.OleDbConnection();
oleMyDbConnection.ConnectionString =
"Provider=Microsoft.ACE.OLEDB.12.0;Jet OLEDBatabase Password=abc;Data
Source=TestDatabase.accdb;Persist Security Info=True";

MyAdapter = new System.Data.OleDb.OleDbDataAdapter();
MyAdapter.SelectCommand = new OleDbCommand("SELECT MyField FROM
MyTable", oleMyDbConnection);

// Try to connect to the database...
MyAdapter.Fill(ds_myDataSet);

When I run it on all Vista machines, it connects perfectly. When I run it on
XP machines, about 90% of machines correctly allow the connection, while
another 10% issue the error "Not a valid password". On these machines, if I
use the same database without a password on the database, it actually
connects (go figure). Users have reported that before September or so, it
ran on their machines, but now it issues the "Not a valid password"
Exception (i.e. an oleDBException). I wonder if some update in XP has messed
this up. This code has run without problem for four years. Now, all of a
sudden, I have an ever-increasing number of users who cannot connect to the
database. Does anyone have any ideas as to what is going on, and even more
importantly, how to fix it?
Thanks.