How can I make my Garmin i2 work again (same as for i3, I guess)?

I seem to have broken my Garmin StreetPilot i2 by adding POIs using Garmin's own software. I think that maybe I've added too many POIs, but the device now won't boot up properly. - it just seize up. Also, since doing this my PC doesn't recognise the device when it's connected.

Anyone else had this problem and can suggest a solution?

Thanks,

Anthony