I have a database made in access 2007 with one subtable refering to another table. Suddenly, It started to only show just 1 tuple related to an especific key of the upper table, and I need to scroll one by one to see all them, it is extremely annoying.

I would appreciate if you help to solve this

Are you accessing this through a set of FORMS or just directly in the Tables? If you are doing it in the tables, I would suggest that you should be working through forms/subforms instead of in the tables directly. Forms give you much more control over what you see than tables and also give you events with which you can validate data and ensure that your data flow is followed and not bypassed.

http://c0013494.cdn1.cloudfiles.rackspacecloud.com/x2_2c0ffb2

This is what is happening, it also ocurring with forms

You need to use forms and subforms (not subdatasheets). It won't happen with forms if you use true subforms and not subdatasheets). You can have the subform be displayed in datasheet view but it is different from using a subdatasheet. Go into each table's properties while in design view and turn off subdatasheets by setting the Subdatasheet Name to NONE from AUTO.