Did you do any Software Update recently?
I've had almost the same issue on my MBP just now, after updating it to 10.6.8. , I cannot send a simple PDF file via bluetooth on my Nokia mobile, but after trying this simple test, I was able to send once again just like I used to.
1. In Bluetooth Preferences, you might try removing the bluetooth device your having trouble with. Sometimes removing and then adding the device back in can fix things. (IF THAT DIDN'T WORK PROCEED TO #2)
2. Still in Bluetooth Preferences, Click on "Sharing Setup" button and check if your "Bluetooth Sharing" service is ON, if it's not, just click on the checkbox to turn it ON.
3. Try sending file again from your Macbook to your device via Bluetooth.
Hope this helped. =o)
God Bless!