[FFL]

I have a feeling that you used CCC to "clone" your Home folder to your LaCie (probably as a backup attempt). It seems that your computer is getting "confused" and seeing the entire LaCie disk as your "Home" folder when the LaCie is plugged in.

The Desktop folder in your Finder sidebar, lost its custom icon, most likely because your "Home" Desktop may have been un-blessed.

Here's what you do - restart if you've plugged in the LaCie since your last restart. Check your Users folder and make sure that your User has the proper icons on it, and that all your documents and data are up to date (if you've been running with the LaCie hooked up, some of your most recent data may actually be on the external).

Once you are SURE that you have everything on your computer, you should Repair Permissions. Then you should restart.

After you restart, plug in the LaCie and use Disk Utility to reformat. If you can't, then select the disk and Get Info in the Finder, and check the box for Ignore Permissions on this volume.