I cannot get Outlook Express either - since one of the automatic Window Updates. The problem is unspecific.
Microsoft report that it is due to Norton and its Spam controller, but as this is disabled, it cannot be. Can only think it has something to do with either Microsoft updates or BT's spam controller - anyway, it's a damn nuisance.
Came back once and wiped every email from my BT Home page - storing it within Outlook Express, which of course, now doesn't work.
I suppose it might work again when I reinstall everything. Wish I could help you :)