How do you normaly close tekkit and log off? Do you hit Disconnect on the menu, or do you usually just "x" the window closed? If you usually just close the window, you might have corrupted your server login file like Silver did the other week; I can fix that by deleting your login file on the server, but you'll lose your spawn and your current inventory (if you use alch bags, those will retain their inventories thank goodness). If you think that is the case, let me know and I can do that for you (I'll backup that file just in case that's not it).
~Epy