Dmitry,

>Therefore, I am wondering, does VFP 9 have the problem with the FQDN-style UNC sometimes but not all the times? Because, clearly, it does not have the problem all the time. And if this is true, the problem happens sometimes, what could cause the problem happen?
>
>Please let me know what you think.

It sounds, like already suggested, that the error may be related to a network glitch and/or re-connection.

What is the setting of SYS(2450)?