If it is just one report it might be something particular to that user, which therefore has no wider implications. Context3D not available is associated with hardware acceleration being unavailable on desktop, perhaps due to browser/plugin settings when using Flash Plugin, or as the computer's hardware is too old.
I am not sure how it would happen on a phone, especially a fairly normal modern phone. Maybe the user has found a debug/developer setting that disables hw acceleration. Maybe the device has overheated, disabling the GPU, or it is simply broken/needs the OS restored.