OS: Windows 7 - 64bit
The program has some kind of random problem with the file list (in memory?). It's like it's not refreshing properly, even if it appears correctly in the UI.
Effect: risk of confusing files with others. Annoyance, if you notice the error (close Viever, click on other files to somehow "refresh", reopen).
To reproduce:
(I don't get consistent results, sorry)
1- open a folder containing various images, sorted by name, in "Details" view and starting with different letters (e.g: Axxx,Bxxx,Cxxx,Dxxx,Oxxx,Zxxx).
2- rename the start of a file (Cxxx -> Pxxx). Click ENTER to confirm.
3- don't click anywhere else, but just refresh with F5. (the list becomes: Axxx,Bxxx,Dxxx,Oxxx,Pxxx,Zxxx)
4- press ENTER to check the file in the Viewer.
5- move to a previous image (I scroll the mouse wheel up).
6- you should see "Oxxx", but sometimes you'll see "Bxxx" instead! (the position before the renaming)
(even ignoring the Viewer, some positioning problem appears also if you try to select a group with SHIFT+Lclick after point 3)
Actual behaviour (bug): wrong image displayed (or wrong files selected with SHIFT+Lclick)

Expected behaviour: correct file displayed\selected