PDO exception when saving where more than one path section used in alias pattern

I have the current settings:

Default path pattern: [node:title]
Pattern for all Blog entry paths: blog/[node:taxonomy_vocabulary_3]/[node:title]

I can save any type other than blog. Saving a blog entry gives me (with a tag of test_tag):

PDOException: SQLSTATE[22P02]: Invalid text representation: 7 ERROR: invalid input syntax for integer: "test_tag": SELECT base.uid AS uid, base.name AS name, base.pass AS pass, base.mail AS mail, base.theme AS theme, base.signature AS signature, base.signature_format AS signature_format, base.created AS created, base.access AS access, base.login AS login, base.status AS status, base.timezone AS timezone, base.language AS language, base.picture AS picture, base.init AS init, base.data AS data FROM {users} base WHERE (base.uid IN (:db_condition_placeholder_0)) ; Array ( [:db_condition_placeholder_0] => test_tag ) in DrupalDefaultEntityController->load() (line 196 of /srv/www/www.chrissearle.org/htdocs/includes/entity.inc).

Tried changing the pattern to:

Pattern for all Blog entry paths: blog/foo/[node:title]

This gives

PDOException: SQLSTATE[22P02]: Invalid text representation: 7 ERROR: invalid input syntax for integer: "foo": SELECT base.uid AS uid, base.name AS name, base.pass AS pass, base.mail AS mail, base.theme AS theme, base.signature AS signature, base.signature_format AS signature_format, base.created AS created, base.access AS access, base.login AS login, base.status AS status, base.timezone AS timezone, base.language AS language, base.picture AS picture, base.init AS init, base.data AS data FROM {users} base WHERE (base.uid IN (:db_condition_placeholder_0)) ; Array ( [:db_condition_placeholder_0] => foo ) in DrupalDefaultEntityController->load() (line 196 of /srv/www/www.chrissearle.org/htdocs/includes/entity.inc).

So - I note that if I have blog/<something here>/[node:title] then I get an ERROR: invalid input syntax for integer: "<something here>" - doesn't matter if its a token or a string.

Am I missing something obvious here?