Webdav problem with application pool identity and windows authentication

Hi!.

I have a server with several webs (IIS 7.5). Most of them have webdav enabled using windows authentication and they work fine. The problem is there are others that don't work.

Webdav is configured on all of them with windows authentication and authorization to allow all users, and the webdav settings are the same.

Things i've tested:

1. It works with basic authentication on all if i change it, but i need windows authentication.
2. I compared the application pool settings of a web that has it working with one that doesn't work and everything is the same (except the identity, wich is set to applicationpoolidentity, so is different).
3. If i change the apppool on the web that doesn't work to one of a web that works, then webdav works for that web.
4. On a web that doesn't work if i change it's apppool identity from applicationpoolidentity to networkService, webdav works.

So it's something about the identity of the application pool, but i don't know how to allow the applicationpoolidentity to work with windows authentication or why some webs works without doing nothing and others don't.

I hope i explained it clearly.

Thank you.