Issues upgrading from iOS 7.1.2 to 8.1.2 on my iPhone 5c.

I recently returned from a deployment overseas. While I was away, iOS 8 was released and I am now attempting to update my 16GB iPhone 5c from 7.1.2. I have attempted to do this via wifi which gives me an error message reading "Software Update Failed; An error occurred downloading iOS 8.1.2". When I try to update through iTunes, the update file downloads to my iMac, but when iTunes begins to install it, I get an error message that reads "The software for the iPhone 'Mark's iPhone' was corrupted during download". I've also been experiencing the same problem with my iPad 2, though I'm not as concerned about that as I don't use it much these days. Has anyone else been experiencing a similar problem? Any advice is appreciated. Thanks!