Installing the service pack does not fix existing items - it will only prevent a particular scenario from happening again.

This is the description of what was changed in the Inventory release notes:

If you made an item active at a location in the Edit Items function (Location tab) when creating new item and the used the Default, or made the item active in the Item List for Location function, or posted a receipt for that item at a location, the Picking Sequence from the item did not display in the Item Inquiry (Quantities tab) and was blank. There was no problem if you used the Edit Picking Sequences function to set the Picking Sequence.

To fix existing items, you need to re-edit the item, either directly or via the Edit Pick Sequences function, and reset the default pick sequence for the affected location(s).