just plug it into a device without EEPC on (like your blackberry, or personal PC) and format it from there.
I have the same problem with the micro SD-card of my Blackberry and I have the problem with an SD-card which I use in my pc. I'm not able to format the cards, not with the BB or not with the PC, I'm always getting the message that "write protection" is on. Changing the switch to another position doesn't work at all. I looks like the software has made the cards read-only and write-protected which makes it impossible to delete or change data or to format the cards at all.
The McAfee software can cause the PC to consider all cards read-only, to stop you copying files to them, but, we have no such software for blackberrys, and the software does not make any hardware changes to the card.
What security software are you using on the blackberrys?