Do you mean 1) when the splash screen on Logic launch is showing and telling you that it's scanning audio units?
Or do you mean 2) that the auvaltool is validating them every time?
1) Always happens, it's part of Logics' launch sequence, can't be stopped or skipped afaik..
You could shorten it by removing every unused Audio Unit from the Library/Audio/Plug Ins/Components and/or the Users/"you"/Library/Audio/Plug Ins/Components folder.
2) Should only happen when new AU's are installed. If this is your problem, quit Logic, trash the audiounits cache, set Logic to 32 bit mode, launch, let the auvaltool validate all plugins, quit Logic (and set it to 64 bit mode if that is how you use it), relaunch it and see if the problem is now gone.
Why did the chicken cross the Mobius ring?
miMac Intel C2Q 2.5 GHz 4 GB RAM/OS X 7.5/Logic 9.1.8 & 10.0.4/MXL 990/Edirol UA-4FX/E-MU XBoard 49/Akai LPD8