You should not be using development builds. You should be using the recommended build (3.0.4)
Switch the launcher to "Always use recommended builds" and then hit clear cache and try again. If it still isn't working you can wipe your tekkit folder and try again.
Private Mod Note
Rollback Post to RevisionRollBack
Hello gamers, Look at your house, now back to mine, now back at your house, now back to mine. Sadly, it isn't yours, but if you stopped playing overrated FPS' and started playing Minecraft, it could look like mine.