I think something similar happened to me, I cleared Caed nua till level 6 or something and went to another place then stopped playing for few days.
Today when I came back to play few of my characters had lost items ( if I remember correctly they had lost the items are the ones I gained on last time I played ) and all had been reduced to be only few XP away from lvl 6 ( on the last time I played I had gained lvl 6 on all my chars except one. )
Well seems like I have to start over, both my tanks are missing armors and few others are missing weapons etc.
