Gallium Nitrate in Treating Children With Brain Tumor, Neuroblastoma, Rhabdomyosarcoma, Non-Hodgkin's Lymphoma, or Refractory Solid Tumors

DISEASE CHARACTERISTICS: Biopsy-proven rhabdomyosarcoma, non-Hodgkin's lymphoma, or other solid tumor refractory to conventional therapy or for which no effective curative therapy is known Re-biopsy required if disease recurs more than 2 years after initial diagnosis recommended if radiographic abnormalities suggest tumor recurrence within 5 months of completing radiotherapy or chemotherapy PATIENT CHARACTERISTICS: Age: 21 and under at diagnosis Performance status: Karnofsky 50%-100% Life expectancy: More than 4 weeks Hematopoietic: (unless extensive bone marrow involvement) ANC greater than 750 Platelets greater than 75,000 Hepatic: Not specified Renal: Creatinine normal for age OR Glomerular filtration rate at least 50 mL/min per 1.73 square meters Other: Adequate nutritional status No serious uncontrolled infection No pregnant or nursing women PRIOR CONCURRENT THERAPY: At least 2 weeks since other anticancer therapy and recovered Prior radiotherapy or surgery for symptomatic lesions allowed provided site of evaluable disease remains untreated Prior bone marrow or stem cell transplantation allowed No concurrent anticancer therapy