After doing some research I learned that I need bypass capacitors in my circuit: one across the PIC's Vss and Vdd pins, and one across the coil of each relay. I added 0.1 uF caps in these locations as well as across the + and - busses of my breadboard. Adding these caps reduced the erratic behavior of the relays but not completely, and I still can't dial out. The circuit works fine if the phone line is not connected to the circuit. Any thoughts?