Vista WebDAV Problems

Hi,

Does anyone have problems with WebDAV in Vista, especially 
with large files, with large I mean over 10MB. 

I have here only WinXP wich works great with mod_auth_mxfix,
and now the first Vista with Problems with large Files. I seen
2 Problems so far ...

1. Problem

For example, if I want to download a excel file with 13MB
I get the error message from Vista after a while

"0x80070057 the parameter is incorrect." 

Searched the net for this error message, can find anything
WebDAV related only for Outlook and some other stuff.

No messages in the LogFile from Apache.

Does anybody know what that means ... 

2. 

Vista has a feature/bug, when you login to dav.example.com/Project_1
then you see all the other Folders in the root level, for example

dav.example.com/Project_2 and 
dav.example.com/Project_2. 

Wich it shouldn't, because the logged in to Project_1, I assume this
is bug http://support.microsoft.com/?kbid=831805

It floods the error logs with max "access denied" entry ... 

Greetings
Erik