I can't seem to use the vibration alerting mode on my handset, any ideas?
It may be that you need to enable vibration. You can do this by following the below instructions:
From the homescreen press Menu - Settings - Sound - Vibration intensity.
Then slide the bars left or right to change the intensity for various features.
You can also turn on or off 'Haptic' feedback in this menu.
The menu structure will vary from device to device and between software versions.