I have been getting the same error message as well and for me it only started after the HoT expansion. It is happening to me so frequently it is making the game unplayable.
I have stopped playing the story mode all together as the amount of times I have been kicked out of story instance forcing me to do it again is too many to count. PVE is a nightmare especially when I am running content like Tequatl and the game crashes and when I start the client up again I am put in some low population map where defeating tequatl is simply not possible.
I understand that with new expansions especially ones as large as HoT there will be problems but we are nearly a month now into the expansion and these problems still have not been sorted, which I cannot understand. I do not feel I have gotten any value for the money spent on this expansion only frustration.