This error message occurs when your game loses its connection with the World of Warcraft servers. Check the @BlizzardCS Twitter account for the current server status. You can also visit our Technical Support Forums for additional information.
If there are no active server issues, follow the steps in our Troubleshooting Connection and Latency Issues article to resolve this issue. If you still receive this error after troubleshooting, please contact us.
You may also find it helpful to use the self-service option to move your character.
Note: Getting this error during an item restoration on an online character is normal. Simply log back in to retrieve your item(s) and continue playing.