If the script in ASP, which reads and writes on the database, gives this error from time to time: Microsoft OLE DB Provider for ODBC Drivers error '80004005' .....

If the script in ASP which reads and writes on the database gives this error from time to time:
Microsoft OLE DB Provider for ODBC Drivers error '80004005'[Microsoft][ODBC Microsoft Access Driver] Cannot open database '(unknown)'.It may not be a database that your application recognizes, or the file may be corrupt.

It is an error due to the database format.
The error is deceptive as it is intermitted and recurring, giving the impression of asp page functioning from time to time.
That is due to the missing support for the new Mdac Microsoft versions, to the Access® format 97. By changing the database to the 2000 version or the advanced version (2002/XP), the problem resolves itself.

After the db conversion check also the format and the correctness of the connection string to the same.