Patients will be treated on a 4-weekly cycle with a single daily dose of 4 mg of RO5126766 on either the twice weekly (Monday & Thursday) or three times weekly (Monday, Wednesday and Friday) schedule. Six patients will be enrolled per arm and after all patients have received at least one cycle of treatment, safety data and available PK/PD data will be reviewed by the Safety Review Committee (SRC). On the basis of the previous Phase I trial, dose limiting toxicities (DLTs) are not expected at a dose of 4 mg but in the event of ≥ 2 DLT's occurring in (a) the 2 x weekly arm, then no further patients will recruited into that arm and the schedule will not be taken forward to Part II, or (b) the 3 x weekly arm, a single dose reduction to 3.2mg on the same dosing schedule will be implemented and 6 patients enrolled at the reduced dose. If 4 mg given 3 x weekly is considered non-tolerable then the SRC may decide to enrol patients to the 3.2 mg dose level in the absence of dose limiting toxicity.