Maybe it cannot be changed after connection is open? Try to change Visual FoxPro default settings at the environment level and than restore it back.

set default to d:\data\foxpro
lnPacketSize = Sqlgetprop (0,"packetsize")
? Sqlsetprop (0,"packetsize",8192)
? sqlc ('bv1','pduser','pduser')
? sqlsetprop (0,"packetsize", lnPacketSize)

>When I try to set the packet size to a larger size in FoxPro 6.0 Sp5 with the following syntax:
>
>set default to d:\data\foxpro
>?sqlc ('bv1','pduser','pduser')
>
>sqlsetprop (1,"packetsize",8192)
>
>I get the following errors:
>
>Warning: The connection sync/async mode cannot be set.
>
>&
>
>Warning: The connection packet size cannot be set.
>
>Any ideas?
>
>Thanks,