yeah this just happened to me when I entered that system with the word arm in it... the exploration one. That toon appears stuck, but the lowbie I rolled who is still in the tutorial doesn't get this error. That alt logs in just fine
i been getting this randomly throughout the day in different systems, basically i log out and play an alt for 5-10 mins then log back in with my main. What this does is put you back into the block instead of the mission, then i select continue and it all loads fine and i continue on.
not really a solution as its server side issue, but a workaround for us for now.
hope this info helps ya for now.
Edit: this is only happening to me on away missions