Nayr,
I currently have it on the floor in the office. No HID/Fluro ballasts, power mains, etc. that would be suspect.
Icerabbit,
I suspect the cable. So far, prefab cables work in all ports with all cameras. Long custom cables will not work with any cameras, both POE or with power supply added. Shorter custom cables work with all cameras. All POE ports are working. One thing that bothered me several weeks ago is the time it took to boot the Foscam camera on the 40' custom cable. It booted and works flawlessly, without issues, it just took much longer to sync up than a shorter cable, custom or prefab. I've also unplugged all cameras and tested with the single long custom cable, thinking that maybe the POE switch voltage wasn't robust enough for multiple cameras. No luck. POE switch works fine with one 40' custom cable, one shorter 30' custom cable, and a third camera with short custom cable. But, when I use the longer custom cable, I cannot get SAPD. The other cameras continue to work fine.
All custom cables are sourced from the same 1000' spool mentioned previously, and all connectors are from the same bulk supply. I would like to find a local prefab cat6 cable (50' or 100') and give it a try, but don't know where to find one. Any of the box stores sell them? And thanks to everyone for your help.