Also I confirm that for first time since 4th Dec. 2014, I have been able to login and relogin to fi.wikipedia with existing password normally. I validated this during last 30 min with IE, Firefox and Opera browsers with laptop and/or tablet (i.e. in two different operating systems). So, the problem seems to be solved. Thanks a lot!

1. I wonder if something has been done to fix the problem "...the failure is probably in SpecialUserlogin between lines 790-807." reported by User:Legoktm earlier?

User Paju is able to login to fi.wikipedia any time, but only through password change (new temporal password requested & this is inserted & password is changed when login). Relogin with new password fails. However some front line authentication system (by Wikimedia Foundation?) seems to recognize when correct password is inserted (redirect to Wikimedia Foundation Error -message) and when incorrect password is given (normal "Login error. Incorrect password entered. Please try again." failure message due to incorrect passwd occurs in Finnish). User Paju does not have problem in login with sv.wikipedia, en.wikipedia, commons, etc, i.e. problem occurs only with fi.wikipedia.

No merging of my Paju account, please. There are at least two different persons using username Paju in wiki projects. I object merging.

It should be noted that the system seems to recognize when user is using correct password (case 1) and when not (case 2). In case 1, user Paju (fi.wikipedia) is redirected to Wikimedia Foundation Error page, as shown above (or below, for 3rd time). If user Paju inserts erroneous password (case 2), system acts normally and notifies him about erroneous password and requests typing password again. So the problem seems to be somewhere after the initial user recognition.