It so happens that during champion select, the client lags like never before.
I've disabled animations, changed my Laptop's color scheme to Windows XP, set my League client's priority into High... AND IT STILL LAGS.
The lag comes from the Chat in champion select (and more).
Here are my specifications
Intel Pentium(R) Dual Core T4500
64 bit Operating System
Here's a picture of my Laptop