I'd first check the GFI. Depending on the quality, they can degrade pretty fast after installation, especially if they are installed outdoors. I've had to replace a few low quality GFI outlets after only a couple of years, even mounted inside "weatherproof" boxes. If the GFI is good (I use a small circuit tester with three LED bulbs on it that tells you about bad connections), then I'd suggest calling CS. I seem to remember a pretty recent thread here with the same issue, which might have some good info on resolution. Good luck!