Images not displaying once upgraded to 3.5

Hi

I have recently upgraded from 3.4.2 to 3.5 and all of my media and images are no longer displaying in the back end nor are they displaying on the front page or anywhere through my website. I have done the plugins deactivate and reactivate process and this had no affect.

I have read some posts with mixed responses and no real answers to the issue. WordPress people are saying its the the theme developer, when I contact my theme developer they say its the update or installation of 3.5 and that the theme is compatible with 3.5. I have had to restore my whole hosting account to 3.4.2 to get past this issue however one of my sites https://www.matthewdunn.com.au was not so lucky as to have a back up and I am stuck trying to find a solution for this one site.

One post I read on the forum said change your permalinks to anything but postname and this actually worked for one day and then it went back to having no images.

I am not wanting to know who is at fault with this issue I am really just wanting a solution to it. Any help is appreciated I know I am not alone with this issue.