Each time I tried to log onto minecraft I would just get a black screen. I tried to fix this by trying all the methods suggested on the net, but had no joy. But I saw one remark that said even though you may be getting a java error report it may actually be that your graphics card driver needs updating. I went into windows device manager clicked on update and hey presto Minecraft login not a problem. I have win. xp and a Radeon graphics card.