Business RDS display

This morning on the way to work, a problem just ocured on my Business
Radio RDS display.
After I started off, I noticed that the display gone off. To have the
display on again I had to switch de radio off and on. Display remains
on for about some seconds, I think 20 seconds (this is a fixed period).
The same occurs to clock, but when I press the clock button it goes on
and after 20 sec aprox. goes off again. This happens separatly from
radio / clock.
Can you tell me what to do ?

Car: BMW 525TDS / Diesel - 1997 (E39)
PORTUGAL