Validating, doesn't happen.

[Butler]

Blockland refuses to validate my key most of the time I try to play.

[Ad Bot]

[Axolotl]

Download RTB4.

[KoopaScooper]

I believe this was stated before, but I think running Blockland on a macintosh computer with RTB can cause validation and other net objects to screw up.
Try removing RTB.

[Crøwn]

I updated my mac to mac os lion and it fixed this propblem.