Unable to save edited Attribute Text

[rw4]

A particular attribute of an inserted block (title block) reverts back to default text (ie.###) every time I save the drawing after editing it.
I can find no difference in the settings of the attribute compared to the others in the same block.
Does anyone know the cause of this happening?

[RobertB]

You fail to mention what field expression you are using.

Sort of like asking the auto mechanic on the phone what wrong with the car because it is making a funny noise, and you don't even mention what the noise sounds like.

[Opie]

Which version of AutoCAD was this created with? Does it use Multi-Line Attributes? I have seen this with Fields that reference Sheet Set Placeholder text.