Link to iManager takes over original browser window

At first I thought this was a problem with our portal, but I've duped it
with OES2 "welcome" page.

If you click a link to iManager from another web page, (like an HREF or
something), it STARTS to open iManager in another browser window (IE 6),
but then it closes that new window and takes over the original window.

Anyone know how to control this behavior?