Rumor has it that Wilbur 1.77 (out now at your favorite Wilbur distribution point) fixes the latitude shader problem referred to earlier.

The sea fix in PS should just be a matter of putting in a sea texture layer on the bottom and chopping out the sea parts on the other layers. A fix involving Wilbur would be to select the sea areas using Select>>From Terrain>>Height Range with a Minimum of -1000000 and Maximum of -0.00001, followed by Filter>>Fill>>Mound with Minimum Height -0.0001 and Maximum Height -1000 to fill the sea basins. Better results can be obtained on the Mound operation by using the Edit Profile button and setting a Non-Linearity value of 2 to get continental shelf-looking things (a similar result can be obtained by doing a Select>>Modify>>Contract with a value of 3ish before doing the initial mound). If it's a little too harsh of an effect, setting Sea Opacity to 0.5 in the Altitude tab of the shader setup will make the water a little murky.