bul dump check sum error

[karambos2]

I've got a Roland JV 1080 and recently for the the first time ever I got the message "Check Sum Error" when trying to reload a bulk dump I'd saved in my sequencer (Logic). The synth didn't respond to anything - it just kept flashing the message "Check SUm Error" so I eventually switched it off. Then when I switched it on again, the sounds were very strange i.e. there was suddenly lots of reverb and/or delay and/or chorus on patches in my performance where previously there had been none. I didn'T know what to do so I set the synth back to Factory Settings. In the manual it just says you have "correct the check sum".

I scrubbed the bulk dump from the sequencer and recorded a new one. When I played it back to the synth I got the same error message.

My question is: how do I rectify this problem?