Um... Hm... Like... o_o; Okay, so you went to Projects, then Project Properties, then Voices(G) and then you set whatever as the default? Like, you're sure? Because I had that error when I was trying .VSQs. Dx
I don't have any Vocaloid programs though. I asked Sango312, and she told me to just re-download UTAU all over again.
My locale's in Japanese, and my default singer I usually change. I've used tried it with Fuko Zonbi and Nami Utaune who both have Hiragana in their wav. files (The Hiragana isn't from the alias)