Comment # 16 on bug 91656 from Nicolai H�hnle

For what it's worth, a comment in the hack posted on the forum says

"PoE tries to read from and render to a texture at the same time when rendering
the minimap. This happens directly after clearing the fbo to (0, 0, 0, 0) so
bind a dummy texture with that value instead."

So this was either a PoE bug (so-called "feedback loop") or possibly a driver
bug related to clearing a currently bound texture that was fixed recently. In
any case, this seems to be fixed now, so closing this report.