It's been doing it to me too. I got the same IT policy what-not message when I tried to trust it which is weird since I am the original owner and it's been strictly for personal use. I don't even know of any local companies that use them on a BES.
And it's been popping up at random times. I usually see it after I've unlocked my phone though, not while I'm in the middle of something.
LG9100f > 7280 > 8700c > HTC 8525 > HTC 3125 > BlackJack > HTC 8125 > Curve 8130 > Bold 9000 > iPhone 3Gs > iPhone 4 > Torch 9800 > iPhone 4