Mentor / Mentee problems.

Now, I can say for 100% it is a bug (it might be just something I failed to do, or some obscure option that I forgot to click), but it sure has the right flavour, so I post it in this forum.
I'm a new player (migrated after NC West wiped my account) and that means leveling a new character. I got the premium account, got busy grinding, but I just seems to get a mentor.
Several separate tries, on different days ended with the same result: I clicked "OK" on mentee invite request, and nothing happened. Literally. No mentor, but also no error info (like: "You can't accept when you're in combat", or "you must do-that-thing-that-you-need to be a mentee".
While it is not game-breaking, I sure as hell missed a lot of exp and coins, which is something to regret given that I started with 0 adena and items.