It sounds like a noise issue. Perhaps one of your devices is producing more noise than it used to (I've had this happen with CFL bulbs that have started to go bad).
If you can do a "breaker box test" (turning off circuits one at a time to try and find the one that might be introducing the noise), you may be able to filter out the noise (or replace a bad CFL) and fix the problem.
However, you asked about signal boosters.
The best one out there (in my opinion, and I know others here agree) is the XTB-IIR, which is made by Jeff Volp (he is a VERY active forum member here). I bought one from him, and it really does the job!
Here is a link to his XTB-IIR page:
http://jvde.us//xtb/XTB-IIR_description.htmIt does require adding a new double-pole breaker to your breaker box, and some additional wiring, which is best handled by an electrician (or a homeowner who is VERY comfortable working inside the breaker box). However, it is by far the best booster out there, and well worth the money.
Jeff also makes a signal/noise meter, the XTBM (which I don't have - yet). I don't have any personal experience with it, but others here swear by it, and it comes highly recommended as THE troubleshooting tool for tracking down noise and signal issues.
I'm sure others will ring in with more information, but that should be enough to get you started in the right direction.