Java SE (Java Platform, Standard Edition)

Here's the situation:

- We have an Eclipse RCP application that users access from a web site using Web Start.
- The initial screen in the RCP app is a login prompt, which takes the id/pw input and sends it to the server using BASIC authentication (yes, I know this is bad, but we are using Spring httpinvoker on the client side and it's a long story...)
- If the user enters an incorrect password, our security component (Acegi for Spring) sends a 401 response back to the client with exception information we need.
- Here's the problem: for some strange reason Web Start sees the 401 response and displays it's own prompt for an id/pw. This is definitely not what we want to happen.

My questions are: why is Web Start intercepting responses after the client app is launched, and is there anyway to prevent Web Start from displaying the prompt?

Thanks.