Here's some help for you and wizards who need help.
Trying to port to someone often results to preventions. They prevent you porting by saying: "Your friend is in a full instance," even when your friend not in a dungeon or tower. Here's what you need to do to fix it.
1. Go to privacy options.
2. Switch allow friend teleports to NO and press OK.
3. Go back to privacy options again.
4. Switch friend teleports to YES again and press OK.
5. See if your friend is able to port.
This solution was brought to you by Cassandra GriffinDreamer.
I've seen a similiar solution also posted on Diary of a Wizard and Valarian's Pad. It may be posted other places as well.
It definitely doesn't hurt to keep spreading information on how to overcome this bug. Thanks, Cassandra!