World Edit Cui is not working for Forge. The owner has stated that he is having problems making it work.
From his forum post. http://www.minecraftforum.net/topic/885099-mc-146-we-54-cui-gui-visualizer-for-worldedit-v146/
"I've tried it in 1.4.6 and it crashes.
Latest stable version for Forge (v1.4.6) - BROKEN: CUI-1.4.6-Forge.zip
Forge support has been added to the mod, however, there is some odd bug that prevents Forge from seeing that the mod class exists, even though it is actually there. If anyone wants to take a stab at fixing it, by all means. If you can solve it, let me know."
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I installed it and added it to the mods floder and here is my client log.
My Client Log
