If the number 1 slot is empty, press and hold it like you were going to dial your voice mail and you should be asked something like "Assign a Speed Dial to . . .?"
If it doesn't do that, make sure you have your own listing in your contacts, go into your call log, click the trackwheel and select View Speed Dial List. Highlight the slot you want to assign a new speed dial to, click the track wheel and select New Speed Dial. Find your contact listing and click on it. That'll do it.
Update: Sorry! These instructions may vary slightly on the 8100 model, but they should be pretty close.
Press your green phone button to get to the calling screen, then press the menu button. Go to options and then you should see a Voice Mail selection. Is there a number there? If not, key in your voice mail number and see if that works.
kasperapd, the voice mail number was configured in the phone.
But guess what? Without me doing anything specific it appeared back in the 1st speed dial slot.
I was turfing some of the alternate input languages and had to restart the Pearl. When it powered back up I noticed that my voice mail was back in slot #1. Maybe the Pearl updates SD automatically if the 1st slot is empty?
I had this exact same problem, but it didn't fix itself like yours did.
i did what you guys said - went to the address book - then to speed dial list and then selected #1 it brought up my address book again and asked who I wanted in there but at the top there was an entry called *use once* i selected that and put in my digits and it works perfect.