For renaming single files, implement a inline renaming feature similar to Windows Explorer, rather than renaming through an edit box.

Details are greatly explained here:
http://forum.mepiscommunity.org/viewtopic.php?p=350208&sid=3f22020150e5115352220797e2c9e4eb#p350208
that's why (with credit to the forum member there) I want to just copy and paste his post:

Real inline renaming of single files using a series of slow left clicks, without bringing up a secondary dialog. This is the one single thing Win Explorer got right. (secondary dialog could still be brought up by choosing 'rename' from the right-click context menu, for the usual multiple renames, find & replace, etc)

First left click selects/highlights filename. 

Second left click encloses filename in an editbox. For now the name remains selected/highlighted, except for the extension. If you begin typing at this point, old highlited file name is wiped out, except for the extension, and your newly typed characters become the new name -- the extension can also be edited if necessary, it just doesn't get highlighted.

Third left click (if you don't immediately begin typing as above) removes highlighting and instead places cursor in the exact spot you clicked, for more precise editing. Do your editing of the filename, then... 

Click somewhere outside the filename/editbox you have been working in, or press enter. Editbox goes away, file is now renamed.