Good question ;).

Currently, all parts of avast 4 except for the boot-time scanner are ANSI-only, i.e. not Unicode. This is mainly to maintain compatibility with Win9x (which doesn’t support Unicode at all). The boot-time scan, on the other hand, is fully Unicode and should be able to open/scan any file in your system.

In short, you’re right, avast! is not fully ready for the East-Asian market at the moment.

This may change in future versions.

Sorry for that,
Vlk