Does not reliably recognize Kindle Fire

On Mac running OS X Yosemite (was similar behavior under Mavericks) Calibre does not reliably recognize when my Kindle Fire tablet is plugged in.

Sometimes it works, sometimes nothing happens, sometimes it runs the Android Transfer Utility.

Placing Calibre in debug mode gives me the following on a failed attempt:

Traceback (most recent call last):
File "site-packages/calibre/customize/ui.py", line 578, in initialize_plugins
File "site-packages/calibre/customize/ui.py", line 53, in load_plugin
File "site-packages/calibre/customize/zipplugin.py", line 197, in load
File "lib/python2.7/importlib/__init__.py", line 37, in import_module
File "site-packages/calibre/customize/zipplugin.py", line 179, in load_module
File "calibre_plugins.ios_reader_apps.__init__", line 43, in <module>
ImportError: No module named PyQt4.Qt
libpng warning: iCCP: Not recognizing known sRGB profile that has been edited
libpng warning: iCCP: Not recognizing known sRGB profile that has been edited
libpng warning: iCCP: Not recognizing known sRGB profile that has been edited
Device 0 (VID=1949 and PID=000c) is a Amazon Kindle Fire (ID4).
FFDL:DEBUG:calibre_plugins.fanfictiondownloader_pl ugin.ffdl_plugin(158):Plugin FanFictionDownLoader macmenuhack file_path:/Users/mfulton/Library/Preferences/calibre/plugins/fanfictiondownloader_macmenuhack.txt
PTP_ERROR_IO: failed to open session, trying again after resetting USB interface
LIBMTP libusb: Attempt to reset device
inep: usb_get_endpoint_status(): No such file or directory
outep: usb_get_endpoint_status(): No such file or directory
2014-11-01 21:03:08.674 Calibre[1237:432021] deliverNotificationWithTitle()
* Notification delivered.


Clearly, the lines starting with PTP_ERROR_IO and LIBMTP suggest that Calibre found the device and tried to do something but it failed.