To solve error 315000 (in my case, i was not able to view my/other players' achievement):
1. Completely uninstall your diablo3(game folder, battle.net & blizzard entertainment folder)
2. copy a "flawless" game folder from your friend's computer
3. launch your dablo3
4. in my case this is where u meet error 14009
To solve error 14009 (where you stuck at authenticating credentials):
1. create a new windows account
2. log in to the new account
3. you should be able to launch your diablo3 without problem
4. log off or switch back to the previous account
5. you should not see error 14009 again
This solution works for win7, I don't know about winxp, but from what i heard: replace your cache folder under blizzard entertainment with a new one works.
I hope my solution helps, I have not enjoyed writing this thread because this suppose to be blizzard's responsibility yet they ignored so many people's thread on this issue.