As I've mentioned, we are currently submitting our application for Vista Certification, and one of the tests we have to pass is that it supports Unicode.

Although the program itself is fine, being a .NET application, our test teams discovered a problem when trying to install to a directory which contained non-Latin characters.

Our installer modifies an XML document, and this is where it fails.

To isolate this problem, we wrote a test install that used the IS XML action to modify an XML file in the install dir.  Sure enough, when we installed it to a directory containing Japanese characters, it reported the same error.

After consultation with Acresso, they have conceded it is a bug in IS.  I'll post news of a patch/workaround if we get one.