With the latest Google Play Update (ver. 4.3.10) it seems to be breaking some of the installs. Users, including myself, are getting "Package file is invalid" errors when trying to download from Google Play.
It seems to be only happening when you try to download large apps, when you receive the warning about it being a large file and suggesting that you use Wi-Fi to download that app. Google knows about it and says "We’re currently investigating a permanent solution, and there are no workarounds at this time."
People have had some success by using the Google Play Website to install the app, and some also have been able to clear their caches on the Google Play Store app and it worked. Neither have been a success for me :(
If you have had the same problem, I guess we just wait.
Update: Google has just recently updated the Google Play Store to version 4.3.11 which has seemed to fix the "Package file is invalid" error. The issue has also been moved to the 'fixed' area on the Google support website. If you are still having problems, try clearing out your cache and reboot your phone.