I am new to nvu and also new to web publishing. I just signed up for a site and received a password with a '%' character in it. The "publish settings" password entry line tries to treat the two characters following the '%' as hex and translate the three characters into a single ASCII character. Workaround: I substituted '%' for the single '%' in the password line.
I don't know if this is a bug or a feature, but I've reported this to the nvu developers.