Cisco Wireless :: Strange Power Failure With AIR-AP1231G

I'm having the following issue with a couple of 1231's.
 
Some overall config info first:
 
This is a small office with 2x Catalyst 2950 (24-port, no PoE) switches and 4 AP1231G (autonomous). The APs get PoE from a PWRINJ3 each. The injectors are powered by the AP power supplies. Injectors and power supplies are mounted in the patch closet.
 
The 2 switches are connected together over 4 ports (20-23 on each switch), these ports are set to 1Q Trunk mode.
 
The APs are connected to the switches, 2 to each switch, on port 1-2. These ports again are configured as 1Q Trunk.
 
APs are connected to the switch as follows:
 
   [switch] <- patch cable-> [injector] <- patch cable -> [patch panel] <- static cabling -> [outlet] <- patch cable -> [AP]
 
All this has been working without problems for a number of years.
 
A few weeks back, AP2 did not restart after a power cut (everything else did). All LEDs are off, port on switch has no LEDs lit. I did not get around to investigating this furtehr until last week. I unmounted (failed) AP2, took it to the spot where (working) AP3 hangs, and plugged it to the cable of AP3. AP2 came to life immediately. I unplugged it and plugged AP3 back in, which restarted immediately.
 
So I suspect a power supply issue on AP2. I took the injector and power supply that fed AP2 out of the patch closet. When connecting AP2 directly to the power supply, it came to life immediately. So I figure the injector is defective.
 
On the same day, I notice AP4 is also dead (again all LEDs off, no idea how long, could have been that day or could have been a few days - it has definitely been working after the power cut that appeared to have killed AP2).
 
So I order 2 new PWRINJ3s and for good measure 2 new power supplies. Later that day, I took the injector and power supply that fed AP4 out of the patch closet. When I try this combination (AP4, injector4 and P/S4), and connect it to a different wall outlet (and therefore a different port -16 - on the switch) IT WORKS! Should have triggered questions, but did not immediately.
 
Last Thursday I got the new injectors and power supplies. So I take one of each, hook them upto AP2 at my desk, and AP2 starts up. So I mount new injector2 and new P/S2 in the patch closet, put AP2 back in its place, connect all the cables - NOTHING. AP2 does not start. The "power" LED on the injecvtor lights up green, the "device status" LED remains off. I take AP2, new injector2 and new P/S2 to my desk, hook them upto a wall outlet (connected to switch port 17). AP2 starts immediately.
 
Meanwhile AP3 has (also) stopped working (no LEDs on at all). As far as I can tell, it stopped working after I briefly disconnected (and reconnected) the patch cable between injector3 and the patch panel in the patch closet. The LEDs on switch port 1 are off.
 
I have since tried to power cycle both switches (took power off both, waited a while, poewerd both back on). No change.
 
PS: the APs ran firmware 12.3(8)-JA until recently. AP1, AP3 and AP4 were upgraded to 12.3(8)-JEE after the the power cut that took AP2 out. THis is when I found out AP2 was dead. AP2 was still on 12.3(8)-JA. It was upgraded to 12.3(8)-JEE last week when it was on direct power on my desk.