device does not appear, though connected

I have a Netgear DG834G wireless router. 3 computers and a printer are
connected to it, and are shown correctly in the "connected devices" config
page.

OTTH, there is also a PDA which apparently works well (Internet connection,
syncing, file sharing -- wirelessly), but it never
appears in the above list.

Is there something I should check?

TIA for advice - regards,

--
Daniel CLEMENT