In the DevForce JetPack Navigation Template, there is a file called CoreStyles.xaml. In this file there is a default style for ListBoxItem. There is a bug in this style.
The issue is that the SL ToolKit has a control called the AutoCompleteBox. This control has a dropdown which shows the items, and the items use the default ListBoxItem style. If the style from the DevForce template is used, the control does not work properly. If the standard SL template is used, it works fine.
To recreate the issue, create a new DevForce Navigation project (I used the JetPack one) and add a AutoCompleteBox which is hooked up to a datasource such as NorthWindIB Customers. Then run the app. Type in a letter, such as G. It will show several items. Then delete the G, and type in E. Instead of just showing the items that start with E, it will show both the E and G items. Continue to do this, and the list just gets longer and longer, the list never getting cleared out.
Now, go into CoreStyles and give the default ListBoxStyle a Key so it is not used in the AutoCompleteBox, and suddenly the AutoCompleteBox works just fine. I really don't know the connection between the two, but it took me quite some time to narrow it down to the template as the source of the problem and I just wanted to pass this on.
Greg