We are seeing very similar issues on our server - players dropping off frequently (3-4 times over a 10 minute span); blocks that were mined reappearing as though they had not been mined at all, players getting killed by mobs while theoretically kicked off the server, and strange elevation changes after returning through a Nether portal. Most critical is the lag, however - last night for instance the lag was so bad it was impossible to attack a mob.
We are seeing very similar issues on our server - players dropping off frequently (3-4 times over a 10 minute span); blocks that were mined reappearing as though they had not been mined at all, players getting killed by mobs while theoretically kicked off the server, and strange elevation changes after returning through a Nether portal. Most critical is the lag, however - last night for instance the lag was so bad it was impossible to attack a mob.