Thanks to CestLaVie for this one:
Windows 2000 Patch: Double-Byte Field Name in an .asp File is Improperly Encoded When Using UTF-8
Microsoft has released a patch for IIS5.0 that addresses a problem that occurs when you save an .asp file as UTF-8 and it contains fields in a form that have double-byte character names, the name is improperly encoded on the server-side when posted.
Read more
Windows 2000 Patch: Double-Byte Field Name in an .asp File is Improperly Encoded When Using UTF-8
Microsoft has released a patch for IIS5.0 that addresses a problem that occurs when you save an .asp file as UTF-8 and it contains fields in a form that have double-byte character names, the name is improperly encoded on the server-side when posted.
Read more