Click on the ICQ flower below any members name to be presented with this screen:
After clicking (Send Message) the next screen you'll see is:
Mirabilis disabled the sending of messages in this fashion some time ago. The result of submitting will always return a 405 - Resource not Allowed error. You should edit your vBulletin 'threads' template to remove the displaying of the ICQ image, at least as a clickable item. You may want to continue to display the ICQ flower to indicate the user has an ICQ number configured in their profile - to alert other users they can view the user's profile for the number.

After clicking (Send Message) the next screen you'll see is:

Mirabilis disabled the sending of messages in this fashion some time ago. The result of submitting will always return a 405 - Resource not Allowed error. You should edit your vBulletin 'threads' template to remove the displaying of the ICQ image, at least as a clickable item. You may want to continue to display the ICQ flower to indicate the user has an ICQ number configured in their profile - to alert other users they can view the user's profile for the number.