IIS webdav and iWork on iOS

Hello

I try to use webdav from an IIS (windows server 2008 R2) server on my iPad because the IIS webdav (like Apache on Linux, but not on 10.7) allow me from an OSX client to make subfolders and rename folders.

Everything seems to work fine, but if I try to save an iWork file as iWork format and open it on my mac, I get error "404, file not found" It work fine with MS Office format and PDF convertions from iWork.

If I try another iOS device with iWork, I can copy the file to the device.

Anyone know if this is because of iOS or does something missing on my IIS installation?