Microsoft Access 2000/XP database is not designed to be used in multiuser server environment. Although Access database can function quite well as a back end for a small ASP site with low traffic, you are always run a risk of database corruption and concurrency issues.
Access databases are known to get corrupted when used under load. Typical symptoms of corrupted database are ASP page timeouts with out any specific error returned. In such case you must download your access database file, open it using appropriate version of Microsoft Access, and run "Compact and Repair". When finished repairing your database, upload your local repaired copy to the web server and overwrite the old one.