Hi Tran,
I cannot say why this is happening but you may want to have a look at our web site
www.stonefield.com. Our Stonefield Database Toolkit has a complete reindexing utility that can be call from your error handler or anywhere else in your application. With a call to this utility the customer doesn't necessarily need to know there was a problem, it just may take a moment or two longer to open the tables.
Yuanitta