[NSGod]

I'm using calibre 2.1.0 on OS X 10.9.4 and the Edit Book.app (as far as I can tell, calibre 2.0.0 also exhibited this behavior).

In the Edit Book app, choosing Tools > Check Book seems to grab (create) 70 to 80 new threads each time it is run, and not destroying them (or reusing them) afterwards. Once the app gets up to around 2000 threads, it ends up bumping up against the 2048 thread limit and I get the error message shown below:

calibre, version 2.1.0
ERROR: Unhandled exception: <b>error</b>:can't start new thread

calibre 2.1 isfrozen: True is64bit: True
Darwin-13.3.0-x86_64-i386-64bit Darwin ('64bit', '')
('Darwin', '13.3.0', 'Darwin Kernel Version 13.3.0: Tue Jun 3 21:27:35 PDT 2014; root:xnu-2422.110.17~1/RELEASE_X86_64')
Python 2.7.8
OSX: ('10.9.4', ('', '', ''), 'x86_64')
Successfully initialized third party plugins: djvumaker && Webscription && Generate Cover && Search The Internet && Open With && Quality Check && Quick Preferences && Resize Cover && Favourites Menu && Barnes & Noble && Find Duplicates && Clipboard Search && Overdrive Link && Goodreads Sync && Modify ePub && Annotations && View Manager && Extract ISBN && Goodreads
Traceback (most recent call last):
File "site-packages/calibre/gui2/tweak_book/boss.py", line 62, in ans
File "site-packages/calibre/gui2/tweak_book/boss.py", line 1052, in check_requested
File "site-packages/calibre/gui2/tweak_book/check.py", line 204, in run_checks
File "site-packages/calibre/ebooks/oeb/polish/check/main.py", line 45, in run_checks
File "site-packages/calibre/ebooks/oeb/polish/check/base.py", line 53, in run_checkers
File "lib/python2.7/multiprocessing/pool.py", line 718, in __init__
File "lib/python2.7/multiprocessing/pool.py", line 159, in __init__
File "lib/python2.7/multiprocessing/pool.py", line 223, in _repopulate_pool
File "lib/python2.7/multiprocessing/dummy/__init__.py", line 75, in start
File "lib/python2.7/threading.py", line 745, in start
error: can't start new thread