Firefox and KDE file associations

I changed the file association for text/html to Firefox, so now when I
click on a hyperlink in an email message the page opens in a new tab in
Firefox.  However, the cursor gets a Firefox icon and another Firefox
button appears in the task list -- as if a new Firefox window were
trying to open.  If I click on the new Firefox button in the task list,
nothing happens.  Eventually, the button goes away and the cursor
reverts.  Is this normal behavior?
-- 
Jeffrey Barish