Filefield with default images passes null value - causing query error

I'm using CCK 6.x-3.x-dev dated 1300406575 including Filefield module 6.x-3.9.

I'm also using Automatic Nodetitles 6.x-1.2.

I've got a filefield that is setup as not required with a minimum resolution and a default image.

Scenario 1
I create a new node, complete the form, select an image that is the appropriate resolution - node is created as expected.

Scenario 2
I create a new node, complete the form, do not submit an image - node is created as expected using the default image.

Scenario 3
I create a new node, complete the form, select an image that is too small - I get an error telling me it's too small. I don't select a new image - I submit the form - I get a mysql error telling me it's trying to insert NULL for the fid in my content type table. Also, a blank node is created with the correct title derived from a CCK text field which is being used by Automatic Nodetitle to create the node title. If I edit the node, the only data that exists in the record is the actual node title, not even the CCK textfield that was used to derive the node title.

Scenario 4
Like Scenario 3 I create a new node with an image that is too small. Instead of just submitting it without an image, I select an image that is the appropriate size - node is created as expected.

The question is, is this a bug? Why doesn't it recognize the form is being resubmitted after an error and now the filefield has no value so use the default image?

Is it the Automatic NodeTitle module? I haven't tried disabling it yet, but perhaps it's trying to create the node prematurely and because the filefield module hasn't told it to use 0 as the fid, it fails when it tries to insert the data into the content type table.

Any help would be great.

Thanks,
Howie