I wanted to post a possible solution to this bug and wanted the developers to see this. When Minecraft is lagging on a good computer (or not) it may be because of java. Control Panel->search for java->go to java tab in popup->view->there will probably be more than one line of code that i assume causes Minecraft to use two different versions of java? When all Java installs are uninstalled and java 6_37 is installed only, Minecraft Runs great. Unknown if it runs well on version 7. When people see a new java update they download and install without uninstalling their previous java version, therefore causing this Minecraft Problem. Maybe Minecraft can be coded to only use the latest java version installed? I hope this information reaches the developers and i hope they make this info more public. Good Luck!