What does: ERROR: tuple offset out of range: 0 mean?

Question

It seems (but I can't tell for sure) that after I added a postgis indexed column (USING gist) to my database last week, I have been seeing a lot of those errors:

ERROR: tuple offset out of range: 0

The errors occur on all kinds of queries, also some that does not use those columns, and hence shouldn't use that index right?

Anyways my question is: What does that error message mean, and could it have something to do with postgis, or am I off track?

I'm on postgresql 9.3 and postgis 2.1