I can't log into various applications

I've got a OnePlus One with CyanogenMod. I've been using it happily for ages but all of a sudden, I can't log into any apps. I'm getting server errors connecting to ebay, ING Bank, citibank, facebook etc. I'm still getting mail but seem to get odd errors on various logins.

I have data and wifi. I'm not in airplane mode and I've tried rebooting my phone. Any ideas?