We had a problem occur with an AP that had 43 associated cpes. About 6 cpes stopped associating with the AP. After several frequency changes the cpes still would not associate even thought the average signal was -70 or better. We swapped cpe at these problem locations with no change, they would not connect.
After disabling EXTENDED RANGE the CPEs would connect. Enable Extended range they would not connect.
These CPEs are well inside 6 miles, bug with extended range feature?
We had been using firm2.2.
We upgraded to 2.3 and enabled extended range feature, ALL GOOD 
Hope this helps anyone out there with similar issues.
turn your extended range OFF
down grade to 2.2
KEEP extended range OFF
re upgrade to 2.3
turn extended range back on.
there is a caution in the release notes to NOT upgrade with extended range enabled.