Sometimes I have problems connecting to www.google.com/adsense using Opera if I am expierencing packet loss. After the packet loss situation clears up I have to close Opera and then reopen it to be able to connect. I find this to be a common trait with Opera and SSL sites.
Check your cookie settings. I've found that sometimes I accidently block cookies that are really needed so that I can log into a website. In Opera go to "File" ==> "Preferences" ==> "Privacy" ==> "Manage Cookies". Look for a entry for "www.google.com" and make sure you haven't blocked cookies for this site.
Nope, it's not that - cookies are enabled. I'll point out the following - it was working - I didn't change any preferences - when I checked a while later I couldn't connect - getting the error I mentioned earlier.
Odd. I have seen reports in different forums of indivduals (presumably MSIE) having problems yesterday and today. Maybe like Google searches, AdSense admin area runs from different data centers and certain data centers are having problems.