I've re-downloaded it, put tons of RAM on it, made sure all my java stuff is up to date, restarted my computer, restarted my internet, I've even downloaded MCPC+ and made it bukkit, and tried many different anti-lag plugins. The "lag" is simply block lag, where we destroy it, and it comes back and needs to be redestroyed, or pops up for a second, and then drops the block.