Can the email attachment image cache be disabled?

I receive email with attached images from a security system with four cameras on a detected alarm event. No problems before update to ios 5. Now the first attachment image received becomes the default image for all camera emails. If I delete the first alarm email, power cycle phone, the next email attachment image becomes the default image. All images are time stamped jpg so no duplicate names to cache on. Because I use Imap, I can go to other computers and the images are correct on those machines. I have another different system that emails attachment jpg images that come through correctly. Only those images are slightly larger in size. 30k versus 19k for the problem emails.