[WJCronon]

To make sure I wasn't misleading anyone, I just completely uninstalled calibre, made sure all files relating to these plugins were deleted, and then installed calibre 2.1 followed by the plugins for IOS Reader followed by Marvin. When I tried to connect Marvin XD on an iPad with calibre, I got this set of error messages (I'm running Mac OS X 10.9.4):

calibre, version 2.1.0
ERROR: Error: Error communicating with device

database disk image is malformed

Traceback (most recent call last):
File "site-packages/calibre/gui2/device.py", line 86, in run
File "site-packages/calibre/gui2/device.py", line 501, in _books
File "/var/folders/vz/zhdqchxj0xv1fb7x_f2_x7nr0000gn/T/calibre_2.1.0_tmp_KumMOu/XwYli7_ios_local_db/Marvin_overlays.py", line 285, in books
File "/var/folders/vz/zhdqchxj0xv1fb7x_f2_x7nr0000gn/T/calibre_2.1.0_tmp_KumMOu/XwYli7_ios_local_db/Marvin_overlays.py", line 2352, in _restore_from_snapshot
File "/var/folders/vz/zhdqchxj0xv1fb7x_f2_x7nr0000gn/T/calibre_2.1.0_tmp_KumMOu/XwYli7_ios_local_db/Marvin_overlays.py", line 2328, in _validate_mainDb_profile
File "/var/folders/vz/zhdqchxj0xv1fb7x_f2_x7nr0000gn/T/calibre_2.1.0_tmp_KumMOu/XwYli7_ios_local_db/Marvin_overlays.py", line 1579, in _compare_mainDb_profiles
File "/var/folders/vz/zhdqchxj0xv1fb7x_f2_x7nr0000gn/T/calibre_2.1.0_tmp_KumMOu/XwYli7_ios_local_db/Marvin_overlays.py", line 2109, in _profile_db
DatabaseError: database disk image is malformed

When I then reinstall calibre 1.48 using the new plugins, I quickly get an "error communicating with the device message," with the following error report:

calibre, version 1.48.0
ERROR: Error: Error communicating with device

database disk image is malformed

Traceback (most recent call last):
File "site-packages/calibre/gui2/device.py", line 86, in run
File "site-packages/calibre/gui2/device.py", line 490, in _books
File "/var/folders/vz/zhdqchxj0xv1fb7x_f2_x7nr0000gn/T/calibre_1.48.0_tmp_bNQ4bz/FVVl3R_ios_local_db/Marvin_overlays.py", line 285, in books
File "/var/folders/vz/zhdqchxj0xv1fb7x_f2_x7nr0000gn/T/calibre_1.48.0_tmp_bNQ4bz/FVVl3R_ios_local_db/Marvin_overlays.py", line 2391, in _restore_from_snapshot
DatabaseError: database disk image is malformed

I hope this helps. Now I have to go back into Time Machine to find the old plug-ins again.