Since you updated the dll, has IIS recycled yet? Also, please make sure that you do indeed have a feedback subject setup correctly. As other users indicated, with the revised dll, the issue is gone, so I'm thinking that in your case either the new dll is not yet loaded or maybe it's not in the bin folder?
Sanjay

Hello,

I've updated the DLL and still I can't edit or reorder either subjects or categories without getting the message:

Input string was not in a correct format.

I tried using both integer and text 'values'; it just doesn't work.

Does this really work for anyone? I just want a feedback form with a selectable subject...

Hi,

I had the same problem.  I created a list of "subject" first and then realized I needed them to be "categories" so that they would be able to direct the email to the proper place.  I didn't receive an error but I couldn't remove the "subject" dropdown.  To resolve this I created a new Subject (also had to make sure it was 'enabled'), selected the new Subject on the Feedback Module settings and then hid it under the settings.  It got rid of it finally.

sounds like a bug. 

Seed