No problem. Sorry it's not working for you yet... but I have a couple of ideas. Let's try this one first :)
Some plug-ins don't like the word "alias" in an alias!!
Do what we did last time (.dat on external drive, create alias, move alias to original location...)
Now, rename the alias file and take out the word "alias" from it.
It should still show the little link arrow on the file icon.
Restart your Mac, start Logic (make sure your external drive is connected first!)
If not, read on....
With some plug-ins, it's important to create an alias of the folder....
So the original location where MSI wanted to copy the .dat and other files to:
Mac HD disk/Library/Application Support/MOTU/MSI
I'm assuming the last MSI in the path is a folder, right?
OK. Copy the MSI folder to your external drive and place the .dat file in the folder (on your external drive).
Move the original MSI folder to your desktop. (backup)
On External drive create an alias of the folder.
Move the alias of the folder to the Original location.
Restart Mac. Make sure ext drive is connected and start Logic.
quit Logic and then rename the alias of the folder and remove the word 'alias'.
Try Logic again.... any joy?
Hope that helps.
The important thing to do is make a clone of your system and / or backup your system before considering re-installing.
Although the .dat file contains all the sounds within MSI, it does not contain any presets or Channel strip settings you've created. You can find these here:
User/Library/Application Support/Logic/ Channel Strip settings/