Custom Item Field on Product Option not displaying

What I need to do:
(see example om this page: http://www.petrockz.net/index.php/shop-online/bonez/product/772-pet-rockz-bonez-large )
1) My client has a product with custom engraved message
2) I have set up Custom Item fields for text boxes to appear on the product page, so customer can enter text to be engraved
3) My client wishes to offer the option to have an additional line of text engraved for an additional price
4) I set up a new 'Optional Extra Text Line' category, created a product 'Optional Extra Text Line' and assigned it to that category, created a Custom Item Field for the text box and assigned it to the 'Optional Extra Text Line' category, finally, assigned this 'Extra Line' product as an option in the product that it applies to.

5) The Option selection box appears on the product page, and when set to YES adds the additional fee for the extra engraving line to the product price, however, the custom item field text box for the customer to enter the extra line to be engraved does not appear.

6) I tested this in my set up phase, and it worked perfectly, with the custom item field text box assigned to the 'Optional Extra Text Line' category appearing just as I wished, when the option on the product page was set to Yes.

7)HOWEVER, now in development phase, when I am setting up products with this option, the custom item field does not appear when the Option is set to yes. The additional fee is added to the product total, but the box to enter the extra line of text does not appear on the product page.

*) I have made every sort of setting change, etc to try and get this to work as it did in my initial test, with no luck

Any suggestions will be greatly appreciated!!!