intermittent dash lights

Any Saab enthusiast ever seen this?

The dash lights only light up intermittently and fade out shortly after coming on ... The mileage is also always dark - here's the clincher - if I unplug the SID the mileage lights up and dash lights work.

Also - when the SID is plugged in and I try to view the miles until empty, it counts in the wrong direction ... i.e. the number of miles until empty increases as I drive (happens quickly)

any advice / help would be greatly appreciated - thanks!