After I had tested (or thought I'd tested) and uploaded the 
Searcharoo version 7 CodeProject article, I deployed 'example code' to 
searcharoo.net, including the 
Silverlight UI. I was shocked and annoyed when it failed to run!
It's worth noting that my hosting provider doesn't server 
.XAP files by default, so of course I had just renamed the 
Silverlightaroo.XAP to 
Silverlightaroo.ZIP, updated the reference in the HTML and expected it would work (like 
Tim says it should).
BUT all I got was 
Microsoft JScript runtime error: Unhandled Error in Silverlight 2 Application This operation is not supported for a relative URI.   at System.Uri.get_Host()

I was confused why this would work fine with 
.XAP but not with 
.ZIP... these are the three scenarios I tried to get it working:
1. <param name="source" value="Silverlightaroo.xap" />This works fine on my local PC, but 
breaks on my hosting provider because the XAP file returns a 404 so the Silverlight application never loads. 
When it works locally, you can see that the 
Application.Current.Host.Source properties are all populated correctly:
 2. <param name="source" value="Silverlightaroo.zip" />
2. <param name="source" value="Silverlightaroo.zip" />Because option #1 doesn't work on my server, I simply renamed .XAP→.ZIP and updated the HTML - but this causes the error shown above. When I debug the Silverlight, the 
Application.Current.Host.Source properties all throw exceptions:
 3. <param name="source" value="http://localhost:3359/Silverlightaroo.zip" />
3. <param name="source" value="http://localhost:3359/Silverlightaroo.zip" />The solution was to use the FULL path to the Silverlight 
.ZIP file, and once again the 
Application.Current.Host.Source properties are populated:

This is not ideal, because now I have to remember to 
change the HTML OBJECT tag "source" PARAM between development/test and production servers - but at least it works! You can 
see the page in action.
Is it just me - or is this a bug?