I encountered an odd and frustrating problem with QGIS and figured I’d post here in case others run into it and need a solution.
Using QGIS 2.4 and 2.6 (both from kyngchaos binaries) under Mac OS-X 10.8.2, if I enable the “Render as HTML” option for a text label in the Print Composer, printing and exporting images of the map no longer works. If I click the appropriate buttons, I can very briefly see the save image dialogue box start to pop up, and immediately disappear. Sometimes, if I click the “Export as image” button several times in rapid succession, the save image dialogue will successfully open. This does not, however, work with the “Print”, “Print Atlas”, or “Export Atlas as images” buttons. Uncheck the “Render as HTML” box, and everything works just fine–well, except that I can’t render html!
I tried a few things: upgrading to the most recent QGIS, downloading various possibly-necessary Python modules, changing various settings that seemed like they might be relevant, and searching online to see if anyone else had solved the problem. No dice… until I changed the blending mode for the text label. It doesn’t seem to matter what I change it to. I can even change it back to the default, “Normal” blending mode. Any change whatsoever to the blending mode fixes the problem. Hell if I know why.