IPAQ not Recognised in Device Manager

I have an Ipaq attached to a Win XP Pro machine but Windows does not
recognize the existence of the device that I can see - there are no entries
in device manager & it does not appear usb root hub. On a few rare
occasions, it does get recognised but comes up as unrecognised device..

I have worked through a number of the troubleshooting posts on a few sites
which have involved soft resets, uninstalling & reinstalling active sync
(4.2)& deleting all USB controller device manager entries but nothing leads to the device being recognised.

The cradle & device have been replaced.

Any ideas??

Thanks