This is a problem with a friend's S3 bought in Hong Kong and used in UK at present on the Vodafone network. She has used the Lookout virus checker from new.
She downloaded a clock app through Playstore, didn't like it, then downloaded another. I do not know the name of these. The phone 'crashed' as she downloaded the second (I wasn't there to see), then when she tried to use Playstore the screen flicked on then off immediately. This has continued. It sounds like the clock app caused the problem and I would like to help her to fix it. Another symptom is that, at times, the phone runs slowly or appears to stop for a while. She has done a full update on the phone's operating system and deleted all updates from Playstore. No good.
One error message that appeared was "Unfortunately the process com.google.process.gapps has stopped".
I wonder if a factory reset would do the trick, but obviously would prefer to avoid the need to reload everything after it.
Hope someone can help