The reason for those newly defined attributes not behaving is explored here:http://usa.autodesk.com/adsk/servlet/ps/item?siteID=123112&id=7586586&linkID=9240817
The text of which is:
When you attached a visibility parameter to one or more block attributes in a dynamic block, the attributes remained visible.
This issue occurs if the Lock position in block check box was not selected when the block attribute was created with the ATTDEF command.
To resolve the problem
In the Block Editor, open the block.
Select the affected block attributes and right-click. Click Properties.
In the Properties dialog box, under the Misc section, change the value of the Lock position to Yes.
Close the Block Editor.
Click Accept to save the block definition.
Note: These changes will only affect new insertions of the block. Block references that were inserted prior to this modification will continue to behave incorrectly.
To avoid the problem in the future, you should make sure that the Lock position in block check box is selected when you create a block attribute (see image below).