Rosebud, I've had the same problem to solve with my rabbits, so I think I can answer your question. Using soft rubber cord covers has not worked well as my buns just chew through them. Also, the sprays that are supposed to deter them have not worked either. I have found one solution that has really worked for us: Fry's electronics carries a hard white plastic wire hider that is meant to "hide" speaker wires (for those with surround sound home theater systems, for instance) that have worked the best for us. If you go to their website and search "wire hider", different sizes will pop up. Once you see what I'm describing, you may be able to find close alternatives elsewhere - I just haven't happened to.
Additionally, when our cable guy came and hooked up our phone & internet, a wire had to be looped through two rooms - he stapled (with a staple gun) the cable to the bottom of the walls. The buns have not chewed on those wires at all, so that may also be an alternative solution if you are comfortable with it (we live in an apartment so don't really care about staples in the walls). Good luck!