Eric,
As Dwayne said, 9600 baud @ 4MHZ is certainely not good.. even worst with the internal one AND by using SERIN. A better practice is to use the internal USART of your PIC and an external Crystal or ceramic resonator.

PIC16F628 have an internal USART, look for HSERIN/HSEROUT

Bonne chance et a bientot!