Editing a book page by another user issues pgsql ERROR: null value in column "log" violates not-null

Error message as follows. Can be re-produced consistently:

Page not found
• warning: pg_query() [function.pg-query]: Query failed: ERROR: null value in column "log" violates not-null constraint in E:\http_root\wiki\includes\database.pgsql.inc on line 138.
• user warning: query: INSERT INTO node_revisions (nid, uid, title, body, teaser, timestamp, format) VALUES (42, 8, 'test', 'testing for other to write. More edits by izmirk Try again to edit', 'testing for other to write. More edits by izmirk Try again to edit', 1206418330, 1) in E:\http_root\wiki\includes\common.inc on line 3303.

This will input a vid value of zero into the node table for that entry, rendering page inaccessible and undeletable.

To temporarily get around this problem (am not sure what are the wider system effects, am new to Drupal):

- Manually input a vid value into the node table to see the page again.
- changed the node_revisions table to allow for null values in column 'log'.

Works for now. Again, am not sure of wider system effects.

SYSTEM
Windows Server 2003
Apache 2.2.8
PHP 5.2.5
Postgresql 8.3.0