Hi, I'm not sure but it could be this.

When I upload my image into the create post edit window I get something like this below:-

!myimage.jpg(WebAddress/RandomnumbersAndLettersImage.jpg)

I change it to this:-

!myimage.jpg(WebAddress/RandomNumbersAndLettersImage.jpg)

So I put [ at the start and ] at the end. Then copy the bit in brackets including the ( and the ) and put it at the very end after the ]

Hope this makes sense and you can get it to work.