iOS 6.1.2 update problems

I have an iPhone 4 and iPad 2. I sync both with my PC and do all iOS and App updates via my PC (because that is where I have free broadband). For some reason I often get the error message “The iPhone (iPad) “[device name]” cannot be updated at this time because the iPhone/iPad software update server could not be contacted or is temporarily unavailable. Please try again later.” It is very annoying. When I try a few days later, it normally works. However, I have found it impossible to update my iPhone’s software ever since iOS 6.1.2 was released. This despite being able to update it on my iPad thru the same PC and exactly the same way I have always done. This is very annoying and really starting to put me off my Apple devices.