Ajax problem with native IE8

I’ve been working on an uploader that stores an image in the database as a base64 encoded string. The upload works fine, and the base64 encoded string is sent back to the browser to display the uploaded image so the user has confirmation that the upload was successful. I test pretty thoroughly using multiple browsers in Windows 7, Mac, and Ubuntu. My Internet Explorer is IE9, and I switch to IE8 browser mode using the developer tools, which also works well. If I use an old Windows XP computer that has native IE8, the confirmation image is not shown. The images are not very large, and the max size is 250kb. Do you think the base64 encoded string is too large for IE8, or is there some other technical reason why IE8 won’t accept the long string? Response is in json format if that matters.

I assume the confirmation images are shown using data URIs?

Does it work if you pretend IE doesn’t support data URIs?

Can you link to a live example?

Yeah it’s just too long – IE8 limits data URIs to 32K