Actually there's no issue with the certificate, some guy or malware on your machinecould be attempting a man in the middle attack!
PLEASE DON'T (AND NEVER) ACCEPT SUSPICIOUS CERTS!
Questions you should ask yourself:
a) Are you using windows?
If so, do you have the latest Security patch installed?
- Malware is very common on Windows, switch to Linux/BSD if you can! :)
b) Who's your ISP?
- It's possible someone has rooted the ISP and is interfering with your traffic.
c) Have you tested this on more browsers?
- There could be a firefox plugin that's messing you up! Try
Google Chrome. It has
some pretty advanced algorithms for detecting phishing.
It could be none of the above though, please get back to us on how you solve this.
Cheers!