the problem is caused by your table relations.
lets take a look at the "Creating Dynamic Menus with CSS Menu Writer 2.0" tutorial on the menu writer support page page in the how to's section:
css-menu-writer/
The sample uses the items and itemcategories table from the Blue Sky music tutorial.
the itemcategories table is the parent table, the structure and data looks like this:
itemcategories:
+-------+---------+
| CatID | Catname |
+-------+---------+
| 1 | CD |
--------+---------+
| 2 | Gear |
+-------+---------+
When creating the first level menu, the CatID column is used for the ID column
the structure and data for the items table looks like this
items:
+--------+-----------+-----------------+
| ItemID | ItemCatID | ItemName |
+--------+-----------+-----------------+
| 1 | 1 | Body Double |
+--------+-----------+-----------------+
| 2 | 1 | So Last Season |
+--------+-----------+-----------------+
| 3 | 1 | HotFlash |
+--------+-----------+-----------------+
| 4 | 1 | A-Go-Go |
+--------+-----------+-----------------+
| 5 | 1 | Filtered Light |
+--------+-----------+-----------------+
| 6 | 1 | DV8: Tendencies |
+--------+-----------+-----------------+
| 7 | 2 | Travel Mug |
+--------+-----------+-----------------+
| 8 | 2 | Travel Tote |
+--------+-----------+-----------------+
| 9 | 2 | Ball Cap |
+--------+-----------+-----------------+
| 10 | 2 | Sport Backpack |
+--------+-----------+-----------------+
| 11 | 2 | Knit Cap |
+--------+-----------+-----------------+
In the filtering section when creating the nested table, the ItemCatID column is selected. that column is used to relate the items to the categories
