Google image bot ignores base href

resulting in 404 errors

[HitProf]

All pages have <base href="http://www.domain.com/"> .
All images are in /imagedir .

64.68.81.xx - - [date & time] "GET /dir/imagedir/image.jpg HTTP/1.0" 404 201 "-" "Googlebot-Image/1.0 (+http://www.googlebot.com/bot.html)"

Pages and images are read fine by browsers and Googlebot/2.1.