Board Thread:Questions and Answers/@comment-92.26.175.168-20121213205916/@comment-5796218-20121214152514

If you're on a valid tekkit server then Hit 'E' first to bring up your inventory and hit 'O' to toggle NEI.

If that doesn't work you might have to delete the tekkit launcher or NEI folders and reload, forcing it to re-build all your prefs again; you may have corrupted the keybinding and there is no way to get to the keybinding section for NEI without first toggling it back on. There might be a cleaner way, but good luck.