SharePoint Designer 2013 crashes when you click "Open Site".
The problem is that the GUIDS in the regristry for SPD 2010 and SPD 2013 open site are the same and it crashes.
Follow these instructions:
Open the Registry Editor. Type Regedit in the windows search.
Look for the keys:
HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Common\Open Find\Microsoft SharePoint Designer\Settings\Open Site
HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Common\Open Find\Microsoft SharePoint Designer\Settings\Open Site
These keys are identical and that is causing the issue. Delete both of the ClientGUID keys by highlighting the key and hitting the Delete key or right clicking and choosing Delete.
This fix worked for me and now SharePoint Designer opens normally.