Image Upload Problem

Hello phpbb3, my site is very heavy on image uploads using the attachment feature of phpbb3.2.1, after the upgrade some members have been contacting me to say there is now a problem when they try to upload images, these images are well within the dimensions I set in the ACP but when some members upload them the software is stating it is far too bit   

One member sent me this image below then I asked him to send me the pics in email and they were actually around 400px by 400px, I tried to upload them to my forum my end and all was fine but he and a few others are getting this issue ?

I have managed to find a temporary fix where by if you save the image as a png / gif you are able to upload the image.