I installed www-client/midori-0.4.6 and tried to download some pdf from a webpage, the grey dialog showed up and midori stopped responding, started using 100% CPU, It was possible to press enter and the download will start, or to close the dialog, it returns everything to normal, but without downloading a file. I asked in #midori on freenode, and I got the answer that it's a glib bug, there is a bugreport against midori on their bugtracker , and on gnome's bugtracker against glib .
Steps to Reproduce:
1. Install midori
2. find page with specific download (now working with every download)
3. click on the download link
Grey dialog showed up, and midori process started using 100% cpu.
Save dialog shown, and be able to save file.
2.32 is in process of being stabilized wrt bug 427544 so backporting to 2.30 is out of question at this point
And midori-0.4.6-r1 from bug 430270 to get fix for bug 422933
Do reopen if the problem persists with the new versions that are going stable