Very odd: most items go thru checkout fine. But a few items cause the entire shipping circuit to fail, and then the dreaded "The shipping rate cannot be determined at this time" appears and no shipping is charged. That just happened, and it cost me $45 in lost shipping charges.

I logged in with a test user id, and built a shopping cart like the one where the shipping failed, and sure enuf it failed for me also. Then I deleted items one at a time and isolated the one causing the problem. I added the rest of the items back in and shipping worked accurately. On the item that failed, I checked it and the shipping weight is fine, so no clue why it's throwing the shipping off. So:

My config:
In Configuration> shipping/packaging I have it configured the heaviest package = 50 and the rest is configured correctly.

For type of shipping I have this:
Zone Based Rates

Enable Zones Method
True

Calculation Method
Weight

Tax Class
--none--

Tax Basis
Shipping

Sort Order
1

Skip Countries, use a comma separated list of the two character ISO country codes

Zone 1 Countries
US,CA

Zone 1 Shipping Table
.1:0,.80:4.00,1.2:5.75,1.5:6.50,1.9:7.50,2.9:9.50,3.9:15.50,5:17.00,6:20.00,7:25 .00,10:35.00,11:36.50

Zone 1 Handling Fee
0

Handling Per Order or Per Box Zone 1 (when by weight)
Order

Zone 2 Countries
AT,BE,BA,BR,BG,CL,CN,FR,FX,DE,GR,HK,IT,JP,MX,NZ,PR,RU,SG,ES,CH,TW,TR,UA,GB,PT

Zone 2 Shipping Table
.1:0,.80:25.00,1.2:26.75,1.5:27.50,1.9:28.50,2.9:31.50,3.9:36.50,5:38.00,6:47.00 ,7:50.00,10:50.00,11:50.50

Zone 2 Handling Fee
0

Handling Per Order or Per Box Zone 2 (when by weight)
Order

Zone 3 Countries


Zone 3 Shipping Table


Zone 3 Handling Fee
0

Handling Per Order or Per Box Zone 3 (when by weight)
Order

Any ideas on why this one item is making the shipping fail would be welcome.
thanks