This has happened to me a couple of times before. No idea how or why.
I go into Links to play an online tourney, click to play a round, and then I'm immediately kicked back to the desktop. I look at my players and lo and behold, my name is missing in Links. I check the player folder on my computer, and the pin file is there. Finally remembering what I had done in the past, I moved the file out of the player folder (place it onto my desktop just in case I need it again), went into Links and rebuilt a player with the same name, and bingo, I'm back to playing online tourneys. Still don't know what causes this.
Anyway, hope this helps someone else with the same issue.