Advanced Search Bug in SharePoint

Recently I was doing some work for a client around setting up an advanced search page and some scopes. The client has several web applications set up and the Shared Service Provider (SSP) is indexing all the web applications. There are several scopes we set up specificly grabbing content from one of the web applications on the SSP. These scopes are set up to grab data that have specific content types.

The problem arose when we tried to set the default scope on the advanced search page. By default the scope for advanced search is All Sites. However when you set the scope to be a custom scope and ensure that no other scopes are active when you return to the advanced search page and search for an item it will return results from every single web application. This is very strange behavior and one which I am curious to hear if anyone has experienced anything like this.

The only way to return items from the custom scope is to modify the advanced search web part and specifically enable scopes on the web part. You then have to select the scope by ticking the check box and click search. I would have thought that by setting a default scope through Site Actions > Site Settings > Modify All Site Settings > Search Scopes on the advanced search section that this would cover it. Maybe there is something I have overlooked. Of course one solution would be to set up seperate SSP's for the web applications but geez I would like to know why it won't work.