there is a red line through the https in the addressbar
A red line through the https on your address bar ... on gmail .... hmmm... doesn't sound good for you. Google doesn't do untrusted SSL certs, so you might well have something on your computer (or elsewhere on your network) doing a MITM attack
I would say assume you've been compromised, use your smartphone or another trusted device on an independent internet connection (e.g. mobile 3G) to change your gmail password pronto (if not all of your critical passwords !).
Do you have a screenshot of said warning and address bar ? Feel free to blur out anything sensitive before uploading.
