Firefox, Chrome or Internet Explorer? Latest versions I presume?
That looks like Firefox's or IE's Anti-Phising. Presuming you have the latest version. I'm unsure why that's appearing. You could delete cookies/cache, just in case an old locally stored file is being referenced. I definitely don't get it.
Does Avast have Anti-Phising? Do you have any other Anti-Malware (AntiVirus/AntiSpyware) software installed? How come btw did you go from Chrome to Firefox? I thought you liked Chrome.
1. Made sure it's the latest version.
2. Deleted Cookies/Cache
3. Does Avast or other software installed have Anti-Phising?
4. Does the error appear in IE? That won't be conclusive as IE uses it's engine from MS but it's still worth a shot.