Diligent Explorer bug

Issue/Problem/Bug: Quest is completed before it should be. Quest log is bugged now.

My computer specs
Operating System: Windows XP


Describe the problem. Be as specific as possible!:
I started the Diligent Explorer quest. I logged off after the three hours on the first day. The second day I returned and decided to try my hand at the PQ Mania medal, so I switched with Delair. Then I decided against it and switched back to Diligent Explorer. Suddenly, there was a book above his head that showed it was a completed quest. So I clicked on him and clicked to complete the quest. Delair said, "Congratulations, you have successfully logged on for... blah blah, Here is your reward!" Then I got an error showing up, "This quest has ended for an unknown reason." Then I d/ced.

I logged back into the game. Now every time I open up the quest window, I d/c. This is really, really annoying.

There should normally be a book above his head in most cases. If you talk to him before you can complete the medal challenge criteria, then you're presented the option to forfeit. Or at least, that's how it was with the Veteran Hunter o.O (and it's now in my quest complete log)

This time however it looks like Nexon phailed.

I bet it has something to do with the quest expiring incorrectly. I was trying to do this quest, logged out about 20 mins after I got it and then logged back in a few hours later the same day and the quest expired when I logged in.

So I guess you forfeit an expired quest and that's causing your error?