Another Attachment Field question

[Ken Horovatin]

I'm having an odd (to me) problem using the AttachmentField in a test
class I've written.
 
My test class is derived from a base class that is derived from the
QMTest Test class. Both my base test class and the test class in
question contain a number of fields, including boolean, text, set and
enumeration fields..
 
The problem is this: the AttachmentField is an optional field, but if I
use the gui to try and create a new test case using my test class, as I
populate any of the set fields, the attachment field displays with a
light red background and displays an "unpack non-sequence" error
message, and I am unable to save the test case.
 
As a very temporary workaround, I'm attaching a dummy file, but this is
obviously not the optimal solution.
 
Any ideas?
 
Cheers,
Ken Horovatin