>To restrict input into a form, I set up combo boxes populated by queries of the main table.
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>When I click the navigation controls I can only move through a few of the records. I can't see any logic to what records appear. If I'm running the 'Set' applet I see the three queries associated with the form, and that my main table is the current table, yet clicking through the records doesn't show each record in sequence. It acts as though a filter has been applied.

Then check the properties of the current table - the little dialogue should show whether you have a filter in effect. Also watch the relations side, you may have a relation set from one of the queries into your current table. Next (and the least probable), check whether your current index is maybe filtered, or even corrupt.