Can't turn pages on 64-bit machine

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Install Visual C++ 2010 x86 runtime on Windows 7 64-bit
2. Run papercrop, open PDF, click on the first page in a vain attempt to give 
it focus
3. Press Down arrow

What is the expected output? What do you see instead?

I wanted to go to the next page so I could process that one.

Instead, the cursor in the options pane on the right (which I don't think 
should be there at all, at the moment) moved to the next option.

What version of the product are you using? On what operating system?

0.51 rev117

Windows 7 Professional x64, service pack 1

Please provide any additional information below.

I *think* this is related to the 64-bitness, but that's strictly a guess on my 
part.

Original issue reported on code.google.com by [email protected] on 6 Aug 2012 at 2:42