Default [Q] Can't install the apps after updating

Friends and developers please help me, i am begging you to solve this problem that
I recently bought my moto E, it was awesome and has 3Gb internal for all storages (Including Music,videos and app too), so i used this mobile to store most of mine apps and by without any external memory card,,
okay
now come to the point,
yesterday i received an OTA software update for mine moto e, so i got much happy about this and so i updated it but after updating it looks so cool than before as usual but when tried to install apps, it's not get installs, it shows an error that 'APP NOT INSTALLED'*.
i got this error for every apps, eventhough my internal memory is having 500mb of free space, but why it happens, what to do to solve this problem,
somebody please help me to solve this,

Thanks in advance