Here's my theory.
Losing in the Super Bowl does not really qualify for "playoff woe" consideration.
IN 2009, the Pats were just a mediocre team by the end of the year, especially without Welker. Getting beaten by a better team does not qualify for "playoff woe" consideration.
In 2010, the Pats made some uncharacteristic mistakes and got outplayed and outcoached by an inferior opponent.
Now, if the 2010 scenario plays out again, then maybe we get into "playoff woe" territory, but as of now, we have a sample size of one abysmal playoff appearance, which doesn't make for a trend and certainly doesn't require a theory of explanation.