Currently, in trunk:

>>> '%0.116x' % 1
'00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001'
>>> '%0.117x' % 1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>

This is intentional, and presumably due to use of a fixed-length buffer somewhere in the formatting internals.  It would be nice (and probably not very hard) to remove this precision restriction.

Looks like I accidentally truncated that traceback.  Here's the full version:

Python 2.7a2+ (trunk:78008M, Feb  5 2010, 23:39:39) 
[GCC 4.2.1 (Apple Inc. build 5646) (dot 1)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> '%0.116x' % 1
'00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001'
[34971 refs]
>>> '%0.117x' % 1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OverflowError: formatted integer is too long (precision too large?)
[35003 refs]

Removing 3.2 from the versions:  the OverflowError appears to be specific to 2.x ints:

>>> '%0.117x' % 1L
'000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001'

Closing:  it's too late for 2.x.