If I were you, I would copy your bin file to your desktop, and then delete it. This will cause Minecraft to re-update back to it's default, unmodded self. Once your running back to the normal minecraft, I would then try and reconnect to a server. If you can connect and don't get disconnected by lag, then I would blame your mods. Only thing I can suggest is either run without mods, or run a search to see if someone has a fix to this: and by google check, I mean the pages for the mods.

dont no try to login with your username or maybe there not runing the server