What you watching it on? I get this problem (if indeed it is a problem) when I`ve switched sources on my LCD. When I go back to the scart (ie from the DVD), I get sound but no picture. Press the scart button again (on the remote) and hey presto picture and sound.
I used to have the Compacks but never had that problem, but it was hooked up to a Sony Wega at the time.