I tried to update my apps today, and there appeared a notice said that "iTunes terms & conditions have changed. Before you can proceed you must read & accept the new terms & conditions". I selected OK and agreed the terms and conditions. Then there was another notice said 'download now: ***will now begin to download'. I pressed Ok. Then the first notice about the iTunes terms and conditions appeared again. All the process repeated then and it became an endless loop. I cannot download or update apps.
This is a widespread issue affecting many iOS devices (with the exceptions of international stores).
update It appears that Apple has resolved the issue. You can now download iTunes media normally.