Are deleting from Outlook on a pc or OWA? Outlook on your pc probably doesn't sync with OWA then your BB. I don't know if there's a fix. Outlook essentially downloads your mail from the OWA Server, for use. It doesn't go from pc to OWA.
I don't know if there is a fix for it. I just live with it. When I'm in the office or working from my home office, I don't need the email on my BB. But I have to go in and manually delete from the BB.