Biomes in the biomelist (/b biome info) are in uppercase with space replaced by "_"
This isn't done for mod added biomes such as ExtraBiomesXL they show up in the biome list but are unuseable because the names are spelled normally

But every mod-added biome(like Woodlands) that doesn't contain spaces in the name works except the ones with spaces in the name when i try that it just shows the last selected biome.

/b biome info shows the mod added biomes just fine btw

Edit: here is a screenshot to explain it better (the marked mod-biomes work just fine)
https://dl.dropbox.com/u/8983610/Pics/Screenshots/Voxelsniper2.png

No. Mod-added biomes are unusable because they do not actually add a biome to Bukkit. (Also, Bukkit does not support any kind of mod officially.) As far as I know they only hook into the biome generator. It's not about spaces.
Spaces are not possible in java names (object, enum, ...) so it is very likely that the mod simply translates the internal names to more user friendly names.

/b biome info reads all available biomes known by Bukkit => only listed biome names are available.

There we go. New build should be up on ci.thevoxelbox.com in a few seconds.

Thanks man ;)

Edit: i think that something went wrong, it still says "Currently selected biome type: PLAINS"
Edit2: oh, every biome doesn't work with the newest build

Whoops. My bad, sorry :( I didn't know, they actually mess with the internal Bukkit enumerations.
It will be fixed in a few minutes.