I bought a Macbook Air back from the refurb store back in January, replacing a Macbook Pro 17" .. Been very happy with the trade, as I didn`t need the power of the 17", and wanted something smaller, but I have major problem with the Air.. It keeps freezing, shutting down Safari and sometimes the whole computer. I`ve always made sure that it`s up to date with software updates, but the problem doesn`t seem to go away. any suggestions?