hi Leatherdale, unfortunately this is likely due to your avast/avg security software tampering with encrypted connections. please either try to reinstall your security software or else follow the more specific steps for it at How to troubleshoot security error codes on secure websites.

Thanks very much. I use AVG and I suppose it was one of their updates that was causing the problem. Anyway I found and unticked the "enable HTTPS scanning" which seems to have done the trick.

I had this problem just after a Firefox update. All sites I tried to get onto including anything via Google and Firefox itself was blocked. As an AVG user I tried the advice above (which I accessed via a different browser) but it failed to fix the fix the problem. I then uninstalled AVG driver scan, started to remove AVG itself but when it offered me the option of repair instead, took that. It seems to have done the trick, fingers crossed!