[Inkscape-user] Dropper not working

For some reason, since I upgraded to the second Beta of 0.45 the dropper tool hasn't worked. I'm running the final version 0.45 and the issue is still present.

With both "Pick Alpha" and "Set Alpha" set it always picks the RGBA value, 00000000. With "Pick Alpha" disabled I get ffffff.

Selecting an average stroke colour works. It's only when attempting to pick a single pixel does it not work.

For some reason, if I search long enough, I can find stray pixels that can be sampled. Not often can I get their true colour though. I can sample colours from bitmaps I use in the drawings.

Any ideas how I can fix this?