This study is for patients with ErbB2 overexpressing breast cancer that has spread to the brain and is still progressing there even after radiation treatment using WBRT (whole brain radiotherapy) or SRS (stereotactic radiosurgery) to the brain. The study will determine how safe and effective lapatinib is when given in combination with capecitabine to treat patients with ErbB2 overexpressing breast cancer that has spread to the brain. Lapatinib is an oral drug that will be taken every day. Tests for safety and efficacy will be performed regularly during the course of the study.