Intermittent crackling noise on surround speakers

My 5 channel system (4 years old) consists of a Rotel 1068 processor, Rotel 1075 amplifier, and Nautilus speakers. For the last 2 years I had only my 803 towers hooked up and everything worked fine. I reconnected all 5 speakers and now there is very loud crackling noise from both 805 surround speakers. The front and center speakers are fine only the surround speakers are affected. The noise is not there all of the time, sometimes it is much worse than others. Any suggestions? Thanks in advance.
I had this problem twice, with two different surround processors from 2 different manufacturers. In both cases, after a lot of testing it came down to a faulty DSP chip in the processor itself. Have you switched cables around to see if the problem follows the connection to rule out a potential problem with your surround speakers and/or your amp channels?
Thanks for responding. Yes, I switched the outputs to my amp and the problem followed so I know it is the processor. I was wondering if there are relay contacts in the output path and the noise is due to dirty contacts. It doesn't happen all of the time. The surround wasn't used for 2 years.
Peb: I'm not sure of the answer to your question. I'd have it looked at and check whether it is still under warranty. Both of the times this happened to me, it was a bad DSP + related circuitry on the board in question; a trip to the repair depot fixed it with no issue.