i've followed the exact instructions on installation on the topic, watched 5 different step by step installation guides, and have even tried using mc patcher to install all the files, and yet i keep getting the same god damn message, even though it seems like this only happens on my computer. i can't even copy the error message because mc closes itself before i have enough time to go ctrl+a ctrl+c.
i may be bitching, but i'm so frustrated with this stuff that i almost threw my mouse after seeing an other error message.
EDIT: these are brand new .jars with nothing added in, although i have removed META-INF.