I'm having this same problem and I don't know how many times I have to do wsreset and or restart my PC to get this to work BUT my problem is not only the Windows 8.1 update. NO NO NO, its every single "app" that I try to install or update...
my system updates are up to date (with no updates available)
my date and time are correct (because I'm one of those strange people that like having my date and time be correct...)
my internet connection is fine.
my anti Virus software is not the problem (nor does it exist)
currently have about 5 windows open trying to fix this problem and my hunch is that the problem is not in my machine!
I have been having these Windows 8 App Store installing/updating problems ever since I bought this Windows 8 PC. I should not have to be looking up resolutions to problems since DAY 1! Seriously Microsoft, Get your stuff together!