attach a file with drag and drop

What steps will reproduce the problem?
1.use keepnote on WINXPSP3
2.when drag the file in to keepnote, nothing happend.

What is the expected output? What do you see instead?
when attach a file with drag and drop on linux, it works well, but on my 
windows xp system, it fails to work.

What version of the product are you using? On what operating system?
0.7.1, 0.7.3

Please provide any additional information below.

Original issue reported on code.google.com by qiaona...@gmail.com on 21 Jun 2011 at 10:39

Merged into: #361

fracte / keepnote

attach a file with drag and drop #489