I think I know the error you have, its a block ID conflict, easy to fix, open the CarpentersBlocks.cfg file and overwrite the Blocks section with this one (I have it on my DW20 pack on my server and client and it works fine :
Code:
####################
# block
####################
block {
I:Barrier=2041
I:Bed=2042
I:Block=2043
I:Button=2044
I:"Collapsible Block"=3518
I:DaylightSensor=2045
I:Door=2046
I:"Flower Pot"=3521
I:Gate=2047
I:Hatch=2048
I:Ladder=3517
I:Lever=2049
I:PressurePlate=2053
I:Safe=3520
I:Slope=2051
I:Stairs=2052
I:Torch=3519
}