Invisible and unselectable flow region in image
I created a PDF with XFig and imported it into Inkscape 0.46 (running on a Mac under OS X 10.5.6, Xquartz 2.1.5 - (xorg-server 1.3.0-apple22) (2.1.5)).
When I uploaded to Wikimedia commons, I noticed a black rectangle; see various versions on http://
I tried various proposed fixes I found on Google: selecting and converting to text; selecting and converting to path.
It took a helpful commons user to find out that the file contains an empty, invisible, unselectable flow region that caused the problem. He or she removed the region using a text editor.