I cannot connect to my server on this version. There is a packet length error I get when connecting.

Server log: http://pastebin.com/2tsTdrcp
Client log: http://pastebin.com/txiRC6bX

Now I am not completely positive it was Mekanism but I just updated only that mod and this happened.

Could you provide both client and server logs?

I have just confirmed it is not Mekanism.