Help! Create folder and upload image in WordPress 3.3.1

I know the problem is discussed for many times, but I have took more than 3 days to try to solve it and I have failed. The details are following:

I have set the file permissions of wordpress, wp-content, and uploads to 777.
I have unchecked the ‘Organize my uploads into month- and year-based folders’ in ‘setting->media’.
In the ‘Store uploads in this folder’, I filled it with ‘wp-content/uploads’.

Now, I can ‘upload’ images in the media page, but it doesn’t have thumbnail. Then I went to the specific folder ‘wp-content/uploads’ and I can’t find that picture.

The apache server is in my local machine.

I closed the security mode of PHP.

I tried to change the file owner and group with root and my another username. I only have these two user accounts in my fedora system.

Yes, I can upload those images manually, but it is really not a good idea and I can not use some plugins which need to create folder or upload images.

Please help me, it is really important to me. Thank you very much.