Had the same problem. I just rebooted my iPhone. I also canceled the remaining downloads and download them again one by one.
Don't worry if you can't download them though. You've bought them and you can download them again via iCloud.
I was so angry that the songs weren't being downloaded that I instead download additional songs thru my iPod Touch 2nd generations. After that, I checked itunes in my Iphone and saw those purchases and the others that couldn't be downloaded. I downloaded them again there. Also, the downloaded songs can be reach via itunes on your computer. Trying borrowing someone else computer.
If they have a computer and it's own iTunes, create a new iTunes that's seperate from theirs via holding on the SHIFT button and click on iTunes. It will ask if you want to create a new one. Do it, but make sure it's located on the desktop so you can delete any of your iTunes information and stuff when you're done. Also, remember to deactivate the connection from your itunes account to that computer.