Your cables may be picking up RF interference form some local source.
Often this will cause the symptoms you describe and it's very difficult to trace, as the interference will vary with weather conditions and local RF signal level.
Interestingly, one cable can cause the problem when to connected different components.
Are your cables original Meridian or some custom cable?

Last edited by shawk; 2008-08-26 00:25. Reason: added info