I created a Christmas card design in Indesign (Just like I did last year with no problems) using CS6 and then exported as a jpg. I just tried to upload to a bunch of different photo printing sites and none of them will complete the upload. Some will upload, but the colors are all inverted so it's useless. I've never had this happen before. I can upload any other images and the cards I made last year, but for some reason not these ones. I know it's not a size issue because they're under 3 MB. Anybody have any ideas?
Check the colour profile. Afaik, such printing sites usually expect RGB color. In case yours are CMYK, that'd explain the false depiction.
They've written it in the FAQs.
You might also want to try exporting to PDF, then convert the PDF in Photoshop if you need jpeg. ID's native jpeg export has never been considered stellar.