Just downloaded the latest nightly (SVN 4681). Completely removed old CodeBlocks folder, unpacked latest nightly, wx dll, and mingwm10.dll into new CodeBlocks folder.
Start page still works. File associations still starts CodeBlocks. However, to check the file associations, I just double-clicked a random .cpp file. This launches CodeBlocks -> Tip of the day -> close. Then I'm left with an empty workspace (i.e. double-clicked item does not show up). If I then exit CodeBlocks it asks to save the changed layout. While the changed layout message is shown, the double-clicked item suddenly (with some delay) appears in the background. If I don't wait for this delay to pass (immediately press No in the save layout message), CodeBlock crashes on exit.
Hmmm, wait, just tried to reproduce the above behavior: I have to say, the double-clicked item does not always appear during the changed layout dialog. But CodeBlocks always crashes on exit when the item didn't show up.
If I can find some systematic thing that triggers the double-clicked item to show up, I'll post again...