Can anyone help?

I am having this problem with my system right now, I was told by my buddy that it is probably my deck causing the problems but im just looking for a second opinion. Latly my back left midrange speaker has been making noise like its blowen but I checked it and its not and every once and awhile my speakers will cut out like the cd is skipping but the deck shows that it is still playing but no sound comming out. Anyone know what could cause this? Thanks