When you use the schema.xml to define a View on a List, each View must have a unique value for the Url attribute. Typically this is in the format Url="/Forms/MyCustomView.aspx".
If you need to add special content or logic to your custom view page, you can simply
- Copy C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\Pages\viewpage.aspx into the same folder where you have your schema.xml file, and
- Rename it MyCustomView.aspx.
- In your List schema.xml file, in the View tag for your custom view, remove the SetupPath attribute. This attribute would normally hijack the URL and point it to the Pages\viewpage.aspx
- Modify MyCustomView.aspx as needed
- Redeploy (as a feature or part of a solution - if the latter, don't forget to add MyCustomView.aspx to your solution's ddf file)