There are two well known issues and bugs about uploading profile pictures to the site system, both of them need some understanding and patience.
One of the problems might happen because the high traffic of the site. Thousands of people signup everyday, hundreds are active every simple and regular day and sevrral upload or change their profile images almost at the same time. This causes high traffic, so uploading anything to the site might cause problems. As you know, this is a basic thing about computers: when the servers are busy - everything becomes much slower and not comfortable.
Also do not forget that the site might have its own bugs and problems which exist a lot of time, you just need to solve it by waiting. As you have probably already seen, near the uploading option it is mentioned that uploading a new picture / replacing your current image with a new picture might take over two hours. This can be cause of: High traffics and busy servers, simple site bugs, and replacement of more than one feature after uploading the picture (as you know, not only the main profile picture changes. The picture in the forums. members list and other places change as well. All of this various changes require extra time for sure).
I am always having this problem when I replace my current picture with a new one, it takes some hours until the picture uploads to: my profile, online members list, forums, etc.
But it never really srucks or stops being in process, but it takes few hours though. But when i upload my first picture, it immediately changes unless my computer or internet connections are slow and take time to let the site webpage load. As I said patience is the key in this case. With enough patience and understanding you will be able to overcome and ger through this issue. Basically, most of the members have the same problem / issue but I would not define that as an issue since it happens to all of us. It is more like a known characteristic of this site. As I said, it is not that hard to wait. You should keep on doing whatever you do here, it will not effect your time here too much.
Another thing that might cause this problem is the unproper picture file. The site accpets only Gpg and Gif files, so please make sure that you have checked the file type and category. If the picture you load does not suit such standarts, then choose a new picture.
If you keep having such problems although you are sure you have done everything properly you should mail one of the moderatprs or the administrator. They should be able to help you get over your issue.