Sometime around my upgrading to versions 2.11 or 2.12 Calibre has been frequently and inexplicably crashing, either while I am manually entering metadata (such as tags) or during the conversion process.
I'm not sure what information would be the most helpful nor where I should provide said info.
I'm using OS X Yosemite 10.10.1; Calibre 2.12 with the following plugins (please see attachment) all updated per the plugin installer: