:::Update:::

Took my bike to my LBS today. Dude was kind of a jerk, refused to look into it but did however offer my money back for the DP18 (he was the one who built it for me and offers a 1 year mechanics guarantee). I declined being the nice guy I am and asked him to install some new rim tape and see if there was a burr underneath. He basically said no. Long story short I went to a different bike shop and bought some new rim tape. Came home, took off old tape, lightly sanded rim, there were a few rough spots for sure....

I then wiped down the rim with a wet cotton ball, followed by a dry one, followed by a fine wool scarf (my girlfriend knitted this for me, ha). I put two layers of electric tape followed by the new rim tape. Installed new tube, pumped to 110 psi and rode 20 miles today without a problem. I do not want to start singing too soon though. After I put 200 miles on it without a rear wheel rim side puncture I will gain some trust again and consider the problem "fixed".

Long story short I am sick of my LBS's and really feel that I need to have the tools and ability to maintenance every aspect of my simple fixed gear myself.

Not a single mechanic at my LBS thought new rim tape was a good idea after multiple flats (bottom of the tube) on a new rear wheel in one month. They did however sell me a new tire and tubes.

Thanks to the posters here for directing me to the possible and likely cause and solution (hopefully).

:::crosses fingers and rides bicycle:::