I don't know if it's related or not but over the last week or so I had a persistent problem where i'd get notified that apps need updating, i'd select the notification and i'd get told there were no updates waiting.

If I looked up an app that I knew needed updating, it'd give me the 'update' button on the app itself.  But I couldn't get a list of apps requiring update.

Reboot no fixy. Nor did hard-stopping the app.

I ended up having to clear the full app cache for the Google Play app to make it work properly again.

I realise this is slightly different to that described in this thread but the timing and the fact it also involves Google Play, seems too coincidental to me.