I didn't do any specific research on the v1280, but a typical "gotcha" when setting up the RJ-45 to DB25 or DB9 connectors is to connect send to send and receive to receive instead of connecting the sends to the receives. For instance,
The typical pinouts for the serial management port go like
Pin 1 RTS
Pin 2 DTR
Pin 3 TR
Pin 4 Ground
Pin 5 Ground
Pin 6 RD
Pin 7 DSR
Pin 8 CTS
So you should make your RJ45->DB25/9 adaptor like...
portcable
RTS -> CTS
CTS -> RTS
DTR -> DSR
DSR -> DTR
TD -> RD
RD -> TD
So when one end sends, the other receives.
Of course, you may already know this, and have made your adaptor correctly. In this case, no harm done. Best of luck! :)
CG