The Edit will be greyed out if SU Podium did not save the image. I have posted similar solution but I'll post this again.
This is also discussed in the FAQ page - http://suplugins.com/podium/image-save-location.php
Skip down the File path length section.
Usual the problem is caused by (rare cases the problem may be caused by your hard disk being full)
1. The name of the path that the image is being saved to is too long or has special characters in it. Characters like ', !!, # in the complete path name can be a problem. Also, if the path name is very long, this can cause SU Podium not to save the image to the custom folder you choose.
2. The model button and the custom button are on at the same time, in the Image Save location. Make sure only one of the options are on. There are some solutions to this issue.
1. Create a folder on your primary drive (for Windows, C:\, for Mac under your user name). Make it an obvious name such as c:\images. The folder must have write permissions in Windows or on the Mac, so make sure you can save files to the folder you want Podium to save rendered images to.
2. In Podium's Options UI, pick the Custom button in the Image save location and then pick the browse button.
Then pick the c:\images folder.
Now try rendering a simple model like a cube and make sure it is getting saved to the c:\images folder.
The Edit menu item in OOPR should also be available.