Once again, don't pay too much attention to the week to week variations. Nebraska rose mainly because my past ballots had them lower than most. Some teams played well and dropped, because they were leapfrogged by better teams. Often bad teams will rise because their strength of schedule suddenly looks better, or other programs played worse.
Most of all, it's just a matter of opinion. C.f. taking months of crap for not thinking USF was any good, even though no one had any qualms with predicting Rutgers to finish last as the result of one bad year. One quick way to see the irrelevancy of polls is to actually try to have to submit one each week when there's little objective criteria to separate one team from the next.