The same thing just happened to me in a completely different world that I was playing by myself. When I had left the game, I was fishing at 130 x 64. When I loaded the game I was falling at -3 x 13. Fortunately this new location was down river, so I landed in the water (thus survived).
I have exited and loaded the game 3 times since without issue - so this is clearly an intermittent issue.
PLEASE CLOSE THIS SPECIFIC TICKET (but not the original). There was a JIRA Website issue - it apparently created two of the exact same issue.
Exact same problem here, but we only started having the problem after the 1.8.0 update - prior versions worked just fine. We even tried creating a brand new world - had the same result. This bug makes playing Minecraft as a family in multi-player no longer viable.