If it (the hum) is not the cable, is there a way to check the dimmer without removing it?
If the dimmer is on a separate circuit, you could probably turn that breaker off, or remove the fuse.
I really like the dimmer - is ther no way to eliminate the hum if the dimmer is the source - other than removing it?
Depending on the brand of the dimmer, I would suggest giving Smarthome.com a call and see if they have any suggestions. I've purchased all of my home automation products from them, and they have very knowledgeable, helpful, customer service.