Totally agree there - there is no way modders would get away with charging for mods; the publishers would be down on your arses in no time (ironically bioware start charging for their NWN mods...)
One of the regulars will be able to fill you in with specific issues, but avoid anything that adds Valygar content or new kits. (Unless you remove old kits first). I think Valen is the only NPC you're adding, and I'm pretty sure she doesn't add music yet so you're ok there...
It's just possible that you have a corrupt sp2 install. Did you use that Microsoft incrimental install thing or did you download the sevice pack as 1 file?