I have a problem similar to the post at http://forums.movabletype.org/2009/11/upgrade-to-5-error-cant-call-method-site-path-on-an-undefined-value-at-libmtupgradev5pm-line-413.html
My installation gets to "Migrating existing 7 blogs into websites and its children..." then I get "Error during upgrade: Can't call method "site_path" on an undefined value at lib/MT/Upgrade/v5.pm line 417. "
The cgi files are all in /cgi-bin/mt/ and the webroot for static files is at /blog/public/. This is an upgrade from 4.2x to 5.
Thanks for any help.
Reported on Movable Type 5
Did you try what the last commenter suggested about where to locate the themes directory?
http://forums.movabletype.org/2009/11/upgrade-to-5-error-cant-call-method-site-path-on-an-undefined-value-at-libmtupgradev5pm-line-413.html#comment-34986