That notice is saying that a lot of Lua errors are occurring, but you have the "Show Lua errors" checkbox unchecked. It's merely warning you that your FPS could drop because a lot of time is being spent handling errors instead of doing what it should be doing.
Most likely one of your addons has a problem in an OnUpdate script or had a problem which triggered the OnUpdate script to fail on every call (such as a variable not being initialized due to an error during startup).
Are you sure it's OmniCC doing this? If you disable it, it goes away? I'm not saying I disagree with you as it is VERY possible for OmniCC to show that problem, but I haven't seen it myself before, and I use it daily.
The one I use is ID 4836, accessible from WoWInterface at
http://www.wowinterface.com/downloads/download4836
If that doesn't work, is it possible the French localization is bad? I would suggest you turn on Lua errors temporarily so you can get and post the error that is occurring.