Hi Jason,
The OverflowError is related to "index-sized ints" as in "ints that are valid indexes for sequences", try:
>>> e = "0" * 1234567890

So it seems that this error is avoiding the creation of a string of length 1234567890, which is a good thing (sorta) :)

Once I tried to implement a dec2long function that was based on numbers instead of strings, see if it helps (it's VERY slow and naive, but IIRC it was a bit faster than the original version and correct): http://groups.google.com/group/comp.lang.python/msg/aba7264ab38eb25e

Now, do you really need all that precision for such huge numbers? I know I didn't ;)
Daniel