Can't update iTunes apps? Here a fix you can try

Something changed over the week when Apple announced the new iPhones and aWatch ... whereby some appstore updates were not working correctly with the following popup appearing in either the iDevice or on iTunes (doesn't matter which platform - tried on OSX and Windows 7/8). The popup has the message "Download for free? This item will be added to your purchases, and will be available even if your Family Sharing status changes" but does not proceed to do anything except loop the message.

The error seems to occur only if you have previously purchased the affected app AND hidden it in iTunes - so for a simple fix, get into your iTunes account management and proceed to the hidden apps, un-hide the app and then proceed with the update as usual. If you don't know how to unhide your apps, then proceed here.