Make sure you are converting a 350AP, and not a bridge.
When using the conversion tool, make sure your vxworks is one of these: (if you have 12.04 you must downgrade)
12.03T, 12.02T1, 12.01T1, 12.00T, 11.23T, or 11.21
SNMP must be enabled.
You can get the conversion tool here:
http://www.cisco.com/public/sw-center/sw-wireless.shtml