Calibre 1.20 After updating, sorting won't work

[Buckshot2]

After searching the posts, I could not find anyone with a similar problem.
I just updated Calibre to 1.20. Everything is fine on my Win8 64bit system. On my Win7 32bit system, every sort returns this error:

calibre, version 1.21.0
ERROR: Unhandled exception: <b>TypeError</b>:slice indices must be integers or None or have an __index__ method

calibre 1.21 isfrozen: True is64bit: False
Windows-7-6.1.7601-SP1 Windows ('32bit', 'WindowsPE')
('Windows', '7', '6.1.7601')
Python 2.7.5
Windows: ('7', '6.1.7601', 'SP1', 'Multiprocessor Free')
Traceback (most recent call last):
File "site-packages\calibre\gui2\library\models.py", line 443, in sort
File "site-packages\calibre\gui2\library\models.py", line 451, in _sort
File "site-packages\calibre\db\view.py", line 262, in incremental_sort
File "site-packages\calibre\db\view.py", line 250, in multisort
File "site-packages\calibre\db\view.py", line 136, in add_to_sort_history
TypeError: slice indices must be integers or None or have an __index__ method

As per the Users Manual, I uninstalled Calibre, made sure the folders were also deleted, then reinstalled - still get the same error.
Does anyone have a suggestion as to what I might try next?

[kovidgoyal]

You appear to have an incorrect tweak setting.

Go to Preferences->Tweaks->Click restore defaults in the top right corner then apply in the top left corner.

[Buckshot2]

Resetting the tweaks back to default fixed the problem.
I had spent several days working on this, and I certainly thank you for the assistance!