Ok I was modifying Tiin's assault to add tons of new ships and I broke the sky, here's the error:

Message Severity: 3
.\Source\LoadUtil.cpp(1010)
Data in C:\Program Files\LucasArts\Star Wars Battlefront II\GameData\AddOn\123\Data\_lvl_pc\123\spa_sky.lvl is not a binary UCF file.

Message Severity: 3
.\Source\LoadUtil.cpp(829)
Unable to find level chunk cor in C:\Program Files\LucasArts\Star Wars Battlefront II\GameData\AddOn\123\Data\_lvl_pc\123\spa_sky.lvl


Message Severity: 3
.\Source\LoadUtil.cpp(1019)
Unable to find level chunk in dc:123\spa_sky.lvl


Also where do I go to fill these two pools:

Message Severity: 2
.\Memory\RedMemoryPool.cpp(170)
Memory pool "ParticleTransformer::SizeTransf" is full; raise count to at least 1039

Message Severity: 2
.\Memory\RedMemoryPool.cpp(170)
Memory pool "ParticleTransformer::ColorTrans" is full; raise count to at least 1538

Message Severity: 2
.\Memory\RedMemoryPool.cpp(170)
Memory pool "RedOmniLight" is full; raise count to at least 153

Make sure you clean and munge. Manually delete your folder from BF2/Gamedata/Addon, make sure you delete the contents of:

data_[mapname]/_BUILD_PC/Worlds/[mapname]/Munged/PC
data_[mapname]/_BUILD_PC/Worlds/[mapname]/Munged/
data_[mapname]/_LVL_PC/[mapname]/[mapname].lvl

(this is a manual clean)

Then re-munge.

Ok. Sky is back. What about those pools?

They're probably automatically filled in regular BF.

Similiar Problem: every time I try to use a sky other than spa_end the game freezes at the loading screen. I tried what Teancum suggested without success. What I'm attempting to do is to change it to the spa_cor sky because it has the most detail. Later on I want to then change the textures of spa_cor to appear like Endor.

You're changing the sky in the LUA, right?

yep