I can see my AP via cdp neigh from the cli of the WLC, but the AP doesnt join to my WLC, whats wrong?
This is a pretty common problem that is usually associated with one of 2 things;
1. The time setting on the WLC and the PC running the upgrade tool (must be in sync).
2. A problem with the SSC (Self Signed Certificate).
Have a look at these great threads from last year that provide answers to both problems.
Here are some excellent docs;
Self-Signed Certificate Manual Addition to the Controller for LWAPP-Converted APs
LWAPP Upgrade Tool Troubleshoot Tips
Lightweight AP (LAP) Registration to a Wireless LAN Controller (WLC)
Hope this helps!