The following text is from the Nikon USA web site and I've included the link at the bottom of this message.
ViewNX 2 is an all-in-one application for image transfer*, browsing, sorting, and quick editing for both still images and movie files. It is a fun and easy-to-use application offering enhanced operation and is useful for all Nikon digital camera owners. Nikon Transfer 2 is included in the application to provide easy file transfer from your Nikon camera* or Memory card reader to a Primary and Backup destination folder. View all images before transfer and select only those you want to keep, rename them, add copyright or other XMP/IPTC information, or Protect your image files from deletion. New editing functions enable cropping and image straightening for RAW-, TIFF- and JPEG- format images, and adjustment of White Balance and Exposure Compensation for NEF/ NRW RAW images captured with Nikon digital cameras. The Picture Control Utility is also included to allow quick modifications of Picture Controls for NEF/ NRW RAW files. View NX 2 will batch convert and/or resize NEF/ NRW RAW files to TIFF(16- or 8-bit) or JPEG quickly and easily. Other editing options include Sharpening, Contrast, Brightness, Highlight and Shadow Protection, D-Lighting, Color Boost, Auto Red Eye Reduction, and Axial Color and Lateral Color Aberration filtering. If more editing is needed, open with Nikon Capture NX 2 with one click on the toolbar. ViewNX 2 is also equipped with new Movie Editor that allows users to trim existing movie files to remove unwanted portions and then compile clips into a single movie with added music and different segment transitions. View NX 2 offers smooth collaboration and easy upload with Nikon Image Space, Nikon's image storage and sharing service. Geo Tag option is fun to add GPS coordinates to your image files and place them on a world map or use the Log Matching function to match image date/time information with GPS log data, then write GPS data to images. *Please note that the transfer function will not transfer images from serial connected cameras. Use of a memory card reader is recommended. This option allows images shot with much older Nikon digital cameras to be used with the latest Nikon software.
I have been using View NX2 10.2 lately because when CNX2 no longer supports a new camera I might buy I won't have to use NX-D which I don't like. I generally only shoot raw but because of your post I tried a few jpg's from different sources.
I find I can view jpg files from a Canon camera, jpg's from a scanner, Nikon files modified by PS CS6 and jpg's modified by Photomatix. I'm running VNX2 10.2 on a 27" iMac.
I have a feeling that your GIMP program is modifying some parameter in the jpg file that 10.2 doesn't like. I don't have GIMP so I can't test it. If you post one of your GIMP modified JPG's to your gallery I can download it and see how it loads on my copy of 10.2.
I use NVNX2 for the majority of my post processing and I have never had a problem opening JPEG files from any source. If you are only having issues with edited images, than that's the source of your problem.
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JL: I have JPEGs generated in FujiFilm FinePix camera, but didn't browse them. Anyway, I had already some JPEGs with the problem.
After installing VNX2 10.2 I didn't process any JPEG, I just open it and went to a folder where I have some JPEGs. Only those saved in GIMP were showing the message if I try to see it in full screen, but still the small view was displayed.
I uploaded 2 photographs into my gallery. You can find them in the "Monochrome" album.
Sunny at Kamba Park Flower spin
JPEG was generated one from View NX2, the black & white from Capture NXD. I added the water mark in GIMP and save.
I could see the small view in VNX2 v10.2 but not large view of them. The large view showed the "unsupported file" message. Then re-installing v9 I am able to see them. Let me know if you are able to see them.