There seems to be a bug that you can do with backpacks and your action bar that causes serious problems. What happens is when you log into servers with this "bagception", doors are unopenable and things cannot be looted. My character cannot be seen by other individuals either (Tested with 3 different friends)
Edit for clarity: other players cannot open doors or loot as well.
In your backpack, fill it up with useables (Food, Water, Weps, Ammo Boxes, Etc). Place these items on #'s 1-9 on the action bar. Then, proceed to hop servers (or find more backpacks in the same server) and put your backpack inside of the new backpack. With this new backpack on you, you can still use the items inside your old backpack cause its considered "on your player".
Proceed to take this backpack and put it inside another backpack over and over again until you can no longer open doors on a new server. This usually happens at a threshold of 10 or so backpacks. Unsure exactly as to when the threshold is met.
This post is related to this Post 0004765: Can not play anymore
This is being caused due to the nesting of the backpacks/containers.
Fix would be to limit bag/container nesting.
If you want to recover your game b/c you did this, Drop some of the nested bags, and join another server and you should be good to go.
Joining any server caused problems. Only solution I had was to lose all my backpacks. The big problem is that it affected the server as a whole as soon as I joined. Seemed weird that it would cause problems to others as well.
We are very sorry, this issue was closed as duplicate.
You can monitor this issue's progress here #1109
I can vouch that this issue caused massive server problems. see issue 0005854 and 0006605