Verify from the inspector that Browse Mode is checked under field entry.
Check also to see if the fields are from the same table occurrence as that specified for the layout or if they are from a related table occurrence. If they are from a related table occurrence issues with the relationship might keep you from editing the fields--particularly if they are empty and won't let you add data into the field.
To check table occurrences and the relationships, enter layout mode and click the field to select it. Note the text to the right of :: in the Display Data From box found on the Inspector's data tab. Then open Layout Setup... and note the exact text shown in "Show Records From". If the text is exactly the same, the field is from the same table occurrence as that specified for the layout and this is not the reason why you are having this issue.
If the names do not match, go to Manage | Database | Relationships. The boxes shown in this tab are what we call "table occurrences". Find the occurrence specified in layout setup and the one specified for the field and investigate how they are related.
Other ways you might be denied access to the field:
If the field is removed from the layout's tab order and a transparent button is placed over the top of the field, then the button will intercept the mouse clicks and prevent entry into the field. A script performed by the button may have used go to field to put the cursor in this covered field and if this script is no longer working correctly, that might be why you can't enter the field.
The file or layout could be damaged in a way that did not create an issue in FMP 7, but does in FMP 11. Try creating a brand new layout without copying any layout objects from the original. See if the field can be edited on this layout. You can also try recovering the file to see if any issues are found by the recover process. Even if no problems were found, test the recovered copy to see if you now can edit the data in these two fields.