Contractor Background and Age
Those are my 2 resume black marks.
Throughout the dotcom era ('96-'01) I worked as a contractor, going from one 6 month to 1 year contract to another. In the bust period I had to scramble for work, doing very short term (2 week to 1 month) contracts, before finding a perm position. Many companies hold this against me.
The other factor is my age, 48. It's easy to figure this out from the resume and I probably don't get called in for several interviews due to this.