So I was playing on my friends server when my inventory started screwing around, in that everything kept jumping around in my inventory and I couldn't place things in a crafting bench. So, as my technologically-declined brain told me to do, PRESS RANDOM BUTTONS! I then activated SensorNet, which I got rid of by clearing the cache, but then whenever I try to log onto Tekkit now, it comes up with the "Updating minecraft.jar x%" bar, then when it's gone to 100% a few times, says "Update Failed!". I reinstalled the launcher a few times, rebooted a few times and changed the data allowance and nothing worked.
I am using Ubuntu and have the latest Java and Minecraft versions.
Help?