A friend had this problem today. Here’s the information I’ve managed to collect.
Error category 4
Error code 1
Out of system resources.
Application failed to initialize.
Try again later.
1. Check firewall configuration and settings (Fireball).
2. Make sure that it allows AIM to connect to the internet.
3. Make sure AIM is on the safelist.
4. Try reinstalling AIM.
Some information from: BigBlueBall Forums – AIM error category 4 code1