Missing Item Error

[Pterosaur]

What has happened here and how do i fix it

[Twisted7]

The model for the item the NPCs are wielding does not exist in your client's data files, or, the display id is incorrect.

Some things I can think of:
-Make sure you are running the same patch version as the server (obviously)
-Make sure the equipmodel1/2/3 entry in the creature_proto table for the affected NPCs is a valid modelID. I'm thinking this is the most likely culprit.
-Make sure your server's DBC files are up to date, existent, and were extracted from the same patch as your users are running.
-If the above does not work, your data files (client-side) might be corrupted. Run Repair.exe app in your WoW directory (be careful, if the data is very corrupted you may have to redownload all patches from 2.0 on).
-If you run Repair.exe and it tells you there is nothing corrupt, try obtaining a new database for your server, or at least new creature_ tables.

Hope this helps.

[TheSpidey]

Nah, not a client error.

If I remember correctly, on 3.0.x, Blizz changed the equipmodel from display ID to actual entry. Try updating your DB with the correct values. Something along the lines of:
UPDATE creature_proto SET equipmodel = (SELECT entry FROM items WHERE items.displayid = creature_proto.equipmodel);

[Twisted7]

There you go, I was sure it was something to do with equipmodel! Spidey's query should fix the issue, though remember to run the query three times with equipmodel1, equipmodel2, and equipmodel3.

[gangstagreen]

Re-import a new and more steady database is another option, there is some great ones in the server releases section. This is just a last resort though.