I had exactly the same problem on my 98 Altima GXE and here is what I gathered.
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Canister vent solenoid is the problem with the Fuel Fill, this takes and vents the vapors and when it goes bad, it will not vent, causing the Gas fill pump to kick off.
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Solution
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In my case the canister vent contol valve was stuck. I had it cleaned and that solved the problem and got me thru the emission test and the pump shutoff is also solved. Here is the link with more info on how to find the evap canister and clean it. Hope this helps.
http://autorepair.about.com/library/a/1g/bl972g.htm