[mbovenka]

Here the tag browser keeps opening. Starting Windows in safe mode doesn't help. The debug log only shows an issue with the Find Duplicates plugin (which works fine regardless):

Spoiler:

calibre Debug log
calibre 4.4 [64bit] embedded-python: True is64bit: True
Windows-10-10.0.18362-SP0 Windows ('64bit', 'WindowsPE')
('Windows', '10', '10.0.18362')
Python 2.7.16+
Windows: ('10', '10.0.18362', 'SP0', u'Multiprocessor Free')
Interface language: None
Successfully initialized third party plugins: DeDRM (6, 6, 2) && KoboTouchExtended (3, 1, 5) && Count Pages (1, 9, 0) && Quality Check (1, 9, 11) && Extract ISBN (1, 4, 4) && Goodreads (1, 4, 0) && KePub Input (3, 0, 0) && KePub Metadata Reader (3, 0, 2) && Webscription (1, 1, 0) && Obok DeDRM (6, 5, 4) && Fantastic Fiction Adults (1, 1, 0) && Manage Series (1, 2, 8) && Barnes & Noble (1, 2, 15) && KePub Metadata Writer (3, 0, 3) && catawiki (0, 0, 2) && KindleUnpack - The Plugin (0, 81, 5) && Fantastic Fiction (1, 3, 0) && Kobo Utilities (2, 9, 0) && BOL_NL (3, 8, 25) && KePub Output (3, 1, 3) && Find Duplicates (1, 6, 4)
calibre 4.4 [64bit] embedded-python: True is64bit: True
Windows-10-10.0.18362-SP0 Windows ('64bit', 'WindowsPE')
('Windows', '10', '10.0.18362')
Python 2.7.16+
Windows: ('10', '10.0.18362', 'SP0', u'Multiprocessor Free')
Interface language: None
Successfully initialized third party plugins: DeDRM (6, 6, 2) && KoboTouchExtended (3, 1, 5) && Count Pages (1, 9, 0) && Quality Check (1, 9, 11) && Extract ISBN (1, 4, 4) && Goodreads (1, 4, 0) && KePub Input (3, 0, 0) && KePub Metadata Reader (3, 0, 2) && Webscription (1, 1, 0) && Obok DeDRM (6, 5, 4) && Fantastic Fiction Adults (1, 1, 0) && Manage Series (1, 2, 8) && Barnes & Noble (1, 2, 15) && KePub Metadata Writer (3, 0, 3) && catawiki (0, 0, 2) && KindleUnpack - The Plugin (0, 81, 5) && Fantastic Fiction (1, 3, 0) && Kobo Utilities (2, 9, 0) && BOL_NL (3, 8, 25) && KePub Output (3, 1, 3) && Find Duplicates (1, 6, 4)
Turning on automatic hidpi scaling
devicePixelRatio: 1.0
logicalDpi: 120.0 x 120.0
physicalDpi: 127.664921466 x 127.590697674
Using calibre Qt style: True
[0.00] Starting up...
[0.02] Showing splash screen...
[0.42] splash screen shown
[0.42] Initializing db...
[30.69] db initialized
[30.70] Constructing main UI...
DEBUG: 0.0 obok::utilities.py - loading translations
DEBUG: 0.0 obok::dialogs.py - loading translations
DEBUG: 0.0 obok::config.py - loading translations
DEBUG: 0.0 obok::action_err.py - loading translations
DEBUG: 0.0 KoboUtilites::action.py - loading translations
DEBUG: 0.0 KoboUtilites::dialogs.py - loading translations
DEBUG: 0.0 KoboUtilites::action.py - loading translations
DEBUG: 43.0 No Kobo Touch, Glo or Mini appears to be connected
DEBUG: 43.0 rebuild_menus - self.supports_ratings=None, self.supports_tiles=None
DEBUG: 43.0 KoboUtilities:set_toolbar_button_tooltip - start: text='None'
DEBUG: 43.0 KoboUtilities:set_toolbar_button_tooltip - setting to text='Utilities to use with Kobo ereaders

Driver: KoboTouchExtended'
Traceback (most recent call last):
File "site-packages\calibre\gui2\ui.py", line 412, in initialize
File "calibre_plugins.find_duplicates.action", line 56, in initialization_complete
AttributeError: 'Main' object has no attribute 'clear_button'
[75.84] main UI initialized...
[75.84] Hiding splash screen
SMART_DEV ( 0.00: 0.001) _attach_to_port try ip address "" on port 9090
SMART_DEV ( 0.99: 0.833) _startup_on_demand listening on port 9090
SMART_DEV ( 1.05: 0.000) _attach_to_port try ip address "" on port 54982
SMART_DEV ( 1.11: 0.000) _startup_on_demand broadcast socket listening on port 54982
[81.58] splash screen hidden
[81.58] Started up in 81.58 seconds with 324332 books
SMART_DEV ( 2.24: 1.073) run All IP addresses {u'{85164C06-C78D-11E7-A876-806E6F6E6963}': [{'broadcast': u'127.255.255.255', 'netmask': u'255.0.0.0', 'addr': u'127.0.0.1'}], u'{C01DB1E2-5444-42B2-9091-21F897BCA924}': [{'broadcast': u'192.168.192.255', 'netmask': u'255.255.255.0', 'addr': u'192.168.192.5'}]}