MrPeanut

Hello , i have the following problem: when i want to play tekkit or any other gamemode in the launcher , i can play these gamemodes only in the version 1.6.4 . The gamemodes works... , but there are a few things i cant do.. i cant sprint , because sptinting was added in a later version. I have absolutely no clue why i cant play it in 1.2.10 or atleast in 1.2.9. Do you have any suggestions for me ? I am using windows 8 , but i dont think thats the problem... sorry for my english , im from germany :-)