Unable to see the audio track wave display

Hi,

I am using Cubase 5. I was able to see the track wave display earlier in the day, but suddenly it seems to have vanished. Now it only displays flat lines when I record or play something. It is not possible to know the progress of the track while playing. I am attaching an image here as well.

Would appreciate if anyone can help.

Regards,
Prem
Track Wave not displayed.jpg