NChibi

Hello, I am trying to play Tekkit Classic on a Mac version 10.8.5 running java version 1.6.0_65. I have re-installed, and re-started everything multiple times (in different versions) and Im still having problems. The problem is that once I enter a world, either on a server or in single player I can move at first but once I stop I can't move anymore, and I can't check my inventory. I can jump by holding the space bar, and I can place blocks and open chests, but nothing else. This is actually not specific to just Tekkit Classic, but also Tekkit Light. I have searched for an answer but haven't found anything. Please help, thanks.