Was it failing at GMail before you flushed at 8.8.8.8? Because then you would have to wait while GMail's own cache expired, assuming they even use the public 8.

Was it failing at GMail before you flushed at 8.8.8.8? Because then you would have to wait while GMail's own cache expired, assuming they even use the public 8.8.8.8 service.