You appear to be suffering from the GUI lag bug that affects some people.. It can happen to those running OS X SL, Lion and ML.. and Logic 9.1.6 through to 9.1.8
There are many other threads about this issue.. Simple google GUI Issues in Logic... and you will find a bunch of links about this known problem. It does tend to affect LIon and ML users more the SL users but it's not unknown.
There is no known fix at this time... We are awaiting a patch from Apple to resolve the issue.
However, if you can, you could try downgrading your Logic to 9.1.5 (assuming you have the DVD boxed set of Logic Studio to allow you to do this) and see if that fixes it... Install Logic 9.0.0 from the boxed set and then update to 9.1.5 using this link..
10.6.8 and 9.1.5 is considered to be the most stable combination of Logic and OS X out there at this time.
If you downloaded Logic from the App Store then you are stuck with the current 9.18 version of Logic.
Thnx for your reply. I had the lag issue on Mountain Lion. Gave up on ML.
Luckily I still had a complete back up of my Snow Leopard system.
Strange thing is that mac in 32 bit and logic in 64 bit runs smooth.
My UAD plug ins force me to use my mac in 64bit kernel. 32bit audio bridge crahes a lot......
I ll try the 9.1.5 . thnx for the tip!