problems with a field within a block (ACAD2006)

Hi,

In Autocad 2006, I created a block called door_symbol.

door_symbol is comprised of the following:

- a block called door_leaf (comprising some geometry drawn at an
overall size of 1 unit)
- two attributes
- one field, which references door_leaf's z-scale

When I insert this block into a drawing, everything works hunky dory,
however sometimes, when saving, regenerating, or resizing/scaling an
instance of the block, all the geometry and attributes disappear,
leaving me with just the field - now reading 0 or 1 - and some far
flung defpoint thingamies. If I try to insert another instance of the
block, the geometry of all the preceeding blocks returns but the field
now reads '#'. Is this a bug, or have I done something wrong?

TIA