[Zope] PIL errors

[irrational]

When trying to create thumbnails from images using the Zope book example, I 
get an IOError.
This occurs when the image I am trying to thumbnail is larger than about 
200k. Smaller images work fine.
The error occurs after the:  image = Image.open(.....) statement. Any 
statement after that starting with image.xxxxxxxx will give the error.
Exact syntax from zope is:
Error Type: IOError
Error Value: image file is truncated, 15 bytes left in buffer

with the amount of bytes changing depending on the image size.

Is this a PIL error or is something wrong with getting the object from Zope 
( using getattr(objectID) )
Could it be the: original_file = StringIO(original_image.data) call and the 
StringIO object is faulty?
Any ideas?

d