Problem upgrading Mvsion receiver

[DestructoMundis]

Hello all,
my 1st post here and thanks in advance for reading and advising.
I recently purchased a MVision 9085 Combo USB Net Special Edition.
I upgraded it straight away via USB pen to version 6.23 and all was fine; then one night after a few too many beers I downgraded it to 6.17; since then the receiver no longer recognizes any USB devices so I haven't been able to reinstate version 6.23.
I have tried to do a direct internet upgrade via LAN/router but the system refuses to upgrade stating that v6.17 is newer than the one available via direct net upgrade on the Mvision sites.
I have also attempted a LAN upgrade to 6.23 but the machine gives error message "Wrong ROM image".

So I bought an RS-232 Null Modem cable and hooked the receiver to the PC, but although the serial port on the PC is working fine, or so it seems, the connection fails at every attempt.

What am I doing wrong?? ! I am tempted to smash the damn thing! 'O'-red

cheers
D