Phal with brown roots - help for Newbie?

[cardigan33]

Sorry for adding another "help!" cry to the list, and many thanks in advance for any who might share their expertise.

I have a Phal that I bought about six weeks ago. Its once green roots have turned brown in many long sections inside the pot, while the roots above the surface are drying and splitting.

I have images on Flickr, if that helps, but can't link them here because I'm new to the forum. One can find them at oldbakehouse [dot] wordpress [dot] com, though, a site for my other hobby.

The orchid has been receiving good, diffuse morning light. Our house is cool but not cold, and it is dry amid the winter season. I'm wondering if I've been over-watering, among other possibilities... And if now I should repot and trim the damaged roots.