Exclamation mark at events in FCPX

I have rearranged my folders. I moved some FCPX events(the whole folder) from my Mac to my portable HD.

I also changed the name of that folder(just ad "(2)" to the file name since name already was in use).

I open FCPX without problem, but at event, where I choose my clip there`s a exclamation mark on the left side of the event-name.
I can`t see any problem with the event-folder, so why to I get the yellow exclamation-mark?

You can't rename folders, and you have to be careful that you don't have links as opposed to real files.

Always move Events and Project to other drives inside of FCP X (drag and drop in the Libraries). And you may want to consolidate the media in Events first.

Each Event and Project is a unique mini database, with a unique database ID that FCP gives to it. If you copy in the Finder, you end up with two databases with the same ID. Renaming folders has no effect on this, and may cause problems.

Copying them inside FCP allows FCP to give the new copy its own database ID, different from the original. Avoids all sorts of headaches.

The other issue is "links". If you import media into an Event, and do NOT tell FCP to "Copy Media To Event Folder", it creates "link files" inside the Event folder, that "point to" the originals. Manually copying an Event to another drive can break that link. If the originals are moved or deleted, the Event links will never find the originals.

If you look inside an Event folder, inside the Original Media folder, look closely at the icons of those files. If there is a tiny little hooked arrow at the bottom left, it is a link, not the original file.

Here's the user manual with some info.
help.apple.com/finalcutpro/mac/10.0.6/#verd1f975b0