This is most likely a PHP limitation, not WordPress one.
The following php.ini directives could all have something to do with it: upload_max_filesize, post_max_size, max_input_time, and memory_limit
For the most part, you are at the will of your host as far as these are concerned.
Technobable aside, my advice is: Try uploading the images (through wordpress) one or two, maybe more, at a time.
I know, that sucks. But, because you want to upload 8MP images, which can be big (3-7MB depending on compression, quality, etc), you MAY be stuck with that.