Yahoo only spiders external.php

I am curious why my logs only show Yahoo spidering external.php. Anyone have a clue?

Search Engine Bots Activity Details - 2005-12-01
SE Bot / Page all Googlebot Yahoo
total 200 170 30
showthread.php 123 123 -
external.php 30 - 30
modules.php 18 18 -
forumdisplay.php 8 8 -
showpost.php 8 8 -
search.php 2 2 -
member.php 2 2 -
index.php 2 2 -
printthread.php 1 1 -
private.php 1 1 -
memberlist.php 1 1 -
faq.php 1 1 -
calendar.php 1 1 -
home 1 1 -
archive/index.php/ 1 1 -

How long have the logs been monitoring? It may just be case that Yahoo hasn't got around to performing a nice sitewide check of your URLs and content unlike Google.

Not that long, I will try to patient and report any change.