I have one form that is bound to a query that brings together 3 tables. The data in all three tables is similar but it needs to be kept in seperate tables.

I thought I could use a tab control to seperate the tables but Access will not let me add to the rcords. All add new record buttons are greyed out.

I know I could use form/subform but I would like to keep the tab control if possible. Anybody ever figured out how to do this?

You could try setting the forms Recordset Type to Dynaset(inconsistent updates).
If that doesn't work then use your approach of updating each record with a different tab, changing the recordsource on the tab change event to the appropriate table (query).

I have updatable queries that join eight tables. It's not the number of tables in the join that causes the problem. Go to the following web site and look for - updatable queries. There are a number of interesting papers available and they should help you identify why your query is not updatable.
http://search.microsoft.com/us/dev/