Buzzing from Input Jack on Rotel Preamp

Hi everyone, hopefully some of you techie experts (Almarg, etc.) can help me out.

My 6-year-old Rotel RC-1082 has developed an immediate loud, constant "buzzing" sound whenever the CD input is selected. I've swapped three different pairs of RCA cables and even tried a different CD player and no matter what, the buzz won't go away. This noise only happens when I have a live RCA feed going into the CD input on the preamp. I've tried wiggling the cables and it sometimes helps, but within a few seconds the buzz comes back. Fortunately, all the other inputs on the preamp work fine. Any idea as to what this problem may be and how to fix it? Thanks.