Assuming its not a bug Judge, have you tried dropping the water a block or two away from the lava and lettign it spread and flow across it?
Hmmm, there seems to be strange things afoot on the server. There are several spots that won't allow you to place blocks, and two places on the minecart track that act as invisible walls. I've tried replacing and rebuilding that spot on the track with no change. Ended up just puttign a loop in the trackway to go around that spot. So at least now it works fine. Game bugs? Server glitches?
Oh also, if you happen to have a minecart in your possession, could you please return it to a station chest? We seem to be running short.