What little thing am I missing that's preventing my bp from eating?

[starfire]

Trying to troubleshoot nuances that may be preventing my 7 year old normal male rescue from eating. I am an older lady with her first snake and on my own here. Suggestions welcome.

History:

Adult male normal bp rescued and rehabbed winter 2008.
Had not eaten for 4 months when rescued; physical trauma and health problems resolved during rehab.
During spring 2008 ate both live and f/t medium rats 1x a week; strong feeding response.
Adopted 7/2008; switched to exclusively f/t medium rats 7/2008 1x a week; no problems, strong feeding response.
Sept. 2008 starting eating only if rat left in tub overnight--shy but ate OK.
Refused food late 10/2008 and did not take food again until 3/2009.

During this time, saw good herp vet; no mites, parasites, RIs, etc. Minimal weight loss during entire fast. Clean and healthy bp.
Vet suggested feeding every 10-14 days once eating again.

Was offered rats every week, then every 2 weeks. Experimented with all of the usual listed sticky suggestions. Also tried supervised live rats, f/t mice. Refused all.

Started eating f/t medium rats again 3/9/2009
Ate 3/22/2009
Refused 4/5/2009, ate 4/12/2009.
Refused 4/26, 5/3, 5/11--ate 5/17/2009
That was the last time he ate to date, over a month ago.

Feeding routine:

No handling feeding day
Fed in his tub
Rats thawed @ room temp and heated by hair dryer or heat lamp before offered with hemostats
Room prescented at least 1 hour

Have tried moving tub location in rack, feeding at different times of day, with light on/off, rat puppet theater action, offering rats from different sources, leaving hides/removing hides, switching substrate to paper towels, switching to appropriately-sized matching round hides. So far, no joy.

Environment:

RBI CB70 3-tub rack heated with two strips of 3” Flexwatt heat tape
Rack housed in a converted walk-in closet; quiet, no traffic, no drafts
12 hours light/12 hours dark
Herpstat thermostat
Acurite thermometer/hygrometer with probe
Radio Shack wireless thermometer
RBI temp gun
Ambient temp: 78-81F
Cool side temps: 79-82F
Warm side temps: 92-94F
Humidity: 60-65% (70s in shed)
Heat supplemented as needed by oil filled heater
Same size smaller black plastic RBI hides both sides
Aspen substrate
Disinfectant: Chlorhexidine gluconate
Cleaning: Tub spot-cleaned daily as needed; complete tub changeout and disinfecting every 10 days
Water changed daily
Handled a couple of times a week for 10-15 minutes when eating on schedule; no handling when not eating

Misc.:

All 4 sheds since 7/2008 have been complete and one-piece perfect.
He thermoregulates appropriately.
Drinks and urinates. No soaking in water bowel.
Has a calm temperament. Alert and responsive but no striking, escaping, or balling up when handled. Good muscle tone and tongue flicking.

Gotta be operator error. I think I have the environmental basics covered, but apparently I'm missing whatever it is that's bothering him. I keep daily records and in review, cannot identify any significant differences in his environment when he's eating and when he's not. Thanks for taking time to read this lengthy post.