I am having a problem with my Galaxy S and Acer A500. I can't download anything from the Play Store, including updates to apps. 

I have done the clear cache thing etc in Applicatons for Play Store and Download Manager and also rebooted both devices. 

The only change I have made in my router which I don't think is the problem, is to add a couple of sites for blocking in my TP-Link 1043ND Access Control settings.  Disabling these also doesn't provide a fix. 

Web browsing on the devices works fine 

Any ideas as its driving me nuts to the cause.