Saw your post before it was deleted Stompa. Try and Google Error 3001. It's been around for quite a few years.

Never really seen an honest cause to it, and there's a myriad of ways to "fix" it. Anything from dcing from your ISP to get a new IP address, resetting your router, file checks, turning everything off and on, logging in your character from another location, moving it out of the affected area, then logging back in on your main computer, etc. There's a large number of things that are claimed to fix the issue. Personally, I got it about a year ago, and after fully shutting down the computer, disconnecting and unplugging the router, and calling my ISP to have my connection re established, I was able to get past the issue.

Alternatively, it seems that if you just wait for 2-3 days, it seems to correct itself.