>Not related to READWRITE because it does not happen with cursors but only on tables opened with USE SHARED.
>Also, not related to right access, because the problem is not always.. and disappears after reboot. I suspect MDAC.
>But don't understand what exactly happen in memory and why.
Could it be temporary lost of network connection? Though the error should be different in this case.
If it's not broken, fix it until it is.
My Blog