What causes 'Unknown token received from SQL Server'?
The error message means client TDS* processing received a token it didn't expect.

This might be a bug, but if so, it is most likely an old one that has long been fixed. You should ensure that the client connectivity components (e.g. MDAC, SQL Server client) are patched up to date (as far as possible, given the old technology).

You should also check that your SQL Server 2005 is running at least Service Pack 4 (though 2005 is out of mainstream support now too).

*tabular data steam; SQL Server's communication protocol