Currently Being ModeratedMay 23, 2013 9:43 PM (in response to Thanos 3)
Did you install T-Racks 3 plug-ins? The error message is probably caused by these plug-ins and not by GarageBand.
"T-Racks 3 TRacks3 Classic EQ has not been properly installed. Please run the installer again to fix the problem"
This means, that the free (?) plug-ins are looking for an installation of the "T-Racks 3 TRacks3 Classic" shell, they will not work unless you buy and install the shell too, afaik. Do you own this program? Then you may need to update "T-Racks 3 Classic". Otherwise the plug-ins will be useless.
I don't own the T-Racks 3 suit, so I cannot check. But to get GarageBand to work, I'd look in the folder /Library/Audio/Plug-Ins/Components on your Macintosh HD in your System Library and remove any Components that are referring to TRacks 3.