Go ahead and head to Admin > Characters and Accounts > Characters and simply delete the duplicate characters, and delete the raids and items uploaded last night.

Then re-import the GRSS Snapshot.

If you don't have the snapshots anymore, you can do a simple character merge of each affected character (merge the new duplicate characters into the original character).

Yesterday, the importer was freaking out and causing duplicates.

Just as a warning to all though, we had someone create accounts with new characters with names very similar to one of our officers. The character made was Nettalia (with a capital "i" instead of the lower case "L"). In the font of our forum, it looks identical and it could have ended up with the imposter being given officer level admin rights on the site.

Make sure you double check before chaning peoples rank that you are sure who it is!