Not sure whether this is a Lesson or a File Picker issue or both.

1.- Lesson settings: Pop-up to file or web page: Choose a file
2.- in File picker: either upload or select from Recent files, e.g. image01
3.- Save the Lesson settings
4.- View Lesson: In the Linked media "block", Click here to view: popup window displays image01 OK.
5.- Edit lesson settings Pop-up to file or web page: Choose a file
6.- in File picker: select a file from Recent files, e.g. image02
7.- after validation, the choice of image02 is displayed in the lesson edit setttings, as expected
8.- Save the Lesson settings
9.- View Lesson: In the Linked media "block", Click here to view: popup window displays image01, not image02 as expected.

Please note that the behavior is erratic, and sometimes it will be possible to select and display correctly a file from the Recent files area, sometimes not...

Bug diagnostic: in the context described, the only way to replace a "media file" to be displayed in the popup window is, in the file picker, to upload a new file, not to select from the Recent files area.

I wanted to test the bug in other parts of moodle 2.0 but it seems that the Lesson module is the only one to "attach" a file in this way. Probably that "Pop-up to file or web page" should be deprecated and removed from moodle 2.0 (or 2.1).