the IT 'Fun Police'
/high fives plant's security team.
Yeah, jamming works at a radio level so you'd expect everything to stop working, must admit i'm not sure though.
This is entirely guesswork but I would guess that the blackberry in particular operates over IP so it is likely that the voice is UDP and the data is TCP since the blackberry server would need a response to know that any emails have been succesfully delivered. It could be that if you are being jammed either intentionally or not, your devices can just about 'hear' the inbound packets but the jamming is strong enough to stop any outbound.
I think it's more likely that 'someone' has accidentally jammed you, I dunno, with a dodgy access point or central heating transmitter or something.