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Please note that the correct answer is 25, and the last element is missing !
This bug does not show on 64-bit versions (but 46337**2 is near 2**31).
~Markus
C:\Python31>python
Python 3.1rc2 (r31rc2:73414, Jun 13 2009, 16:43:15) [MSC v.1500 32 bit
(Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> len(list(range(46337**2, 46349**2, 46337)))
24
C:\Python30>python.exe
Python 3.0.1 (r301:69561, Feb 13 2009, 20:04:18) [MSC v.1500 32 bit
(Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> len(list(range(46337**2, 46349**2, 46337)))
24

Simpler test case:
Py2.6:
>>> n = 46349**2
>>> n
2148229801L
>>> range(n-10, n, 3)
[2148229791L, 2148229794L, 2148229797L, 2148229800L]
Py3.0:
>>> n = 46349**2
>>> n
2148229801
>>> list(range(n-10, n, 3))
[2148229791, 2148229794, 2148229797]

The length calculation in range_iter in Objects/rangeobject.c is 
incorrect, when using a longrangeiterobject. The length is computed
as: (stop - start)//step. It should be ceiling((stop-start)/step), or
1 + (stop - start - 1)//step, provided that start <= stop and step > 0.
It's not clear to me right now whether there may also be problems with 
negative steps, and with cases where start < stop, etc.
I think this is serious enough to be considered a release blocker for 3.1; 
I'm working on a patch, and will post it later today.

Here's a patch for py3k.
There are also a whole bunch of tests that are commented
out in BuiltinTest.test_range in Lib/test/test_builtin.py.
Some of those tests fail with the current py3k; with this
patch applied, they all pass except the one involving 'badzero'.

The patch looks good. Please apply.

Applied to py3k in r73547. Will backport to 3.0.

Backported to release30-maint branch in r73549.
Thanks for catching this, Markus!

Many thanks for your quick fix! ~Markus