This is not a problem in HikaShop.
There are a lot of cases when that can happen:
1. your image is not really a jpg image (like for example if it's a gif and the file extension was renamed to jpg). => correct the extension of your file
2. your image was saved in CMYK format instead of RGB. That can produce problems with some versions of the GD library of PHP which HikaShop uses to resize the images. => save your image in RGB format
3. you use php 5.1.3 or a previous version of php 5. There was a bug in some cases in the way the GD library was used by PHP. =>
bugs.php.net/bug.php?id=29878
you need to update PHP
4. the wrong jpeg library is used on your server =>
bugs.php.net/bug.php?id=50125
follow the recommendations there
5. you can also try to deactivate GD's warnings =>
bugs.php.net/bug.php?id=39918
6. As a last resort, you can disable thumbnails in the config of HikaShop under the tab files. That way, HikaShop won't create thumbnails for your images.
In any case, there is nothing we can do on our end to help you and you will have the same problem with any PHP application on your server if you try to resize that image :/