Today I set up my first NLBd Sharepoint. The problem I had was that when I took down the first installed server the second one did not work. The problem was that the Sharepoint installation did not use the the NLB cluster address, it used the address of the fists server.

The solution is called Alternate Access Mapping. You need to change the URL in alternate access mapping to the Cluster URL. Here is how:

1. Start Central Administration
2. Go to the Operations tab
3. Click on Alternate Access Mappings under Global Configuration
4. You should now see a list of your web applications, switch over to the one you want to map to the new URL by selecting it from the drop down on the right side
5. Change the default field to the NLB address

Links:

http://blog.henryong.com/2007/01/17/alternate-access-mapping-in-sharepoint/