I haven't read Manu's doc but -2 spid is related to MSDTC...
I have had an orphaned spid (-2) previousl and it was related to a (MSDTC) transaction rolling back.
read the article and see if it helps...
Just had a quick scan of the doc and the problem i had was related to this section: Killing an MSDTC transaction
I think the doc should should you out.
Gethyn Elliswww.gethynellis.com