Apache2 and Webdav

Hi,

I use Apache2 "httpd-2.0.59-p+mods-nw.zip" on a NW 6.5 SP5 server with
all
patches. 
Webdav is enabled and works for about 3 to 4 days. After about 4 days, it is
impossible to connect to the Webdav share, the Webdav share cant be found.
Restarting Apache2 did not help, the only solution is to restart the server,
than Webdav works again for about 4 days. 

Any ideas how to get Webdav permanently working?

Walter