Call to undefined function: spam_delete_trackback

I'm having the same problem on some sites I've installed this module on, but not others. On sites that never had the trackback module installed, spam.module doesn't generate this error.

On sites where it was once installed (but is no longer installed) it occurs.

I've tried removing the database tables related to the trackback.module. No luck so far.

OK, I found the source of this error.

Line 462 calls a function based on the value of the column 'source' in the spam_tracker table. If you've upgraded from previous versions of drupal while using the spam and/or trackback modules, it's likely you've got old entries in there with "trackback" as the value for the "source" column.

Spam.module will try to call the function spam_delete_trackback to delete that spam, but this function no longer exists.

Run this SQL query on your database to solve the problem and allow cron to complete:

delete from spam_tracker where source = 'trackback';

dmjossel's manual fix solves the problem. Marking as such.