RATIONALE: The Epstein-Barr virus can cause cancer and lymphoproliferative disorders. Valganciclovir is an antiviral drug that acts against the Epstein-Barr virus. Phenylbutyrate may make cells infected with Epstein-Barr virus more sensitive to valganciclovir. Giving phenylbutyrate together with valganciclovir may block the growth of Epstein-Barr virus-infected cells and kill more cancer cells.