You are having new tests ordered, as well you should be retesting the original sample. Did you give a urine sample or a blood sample?
A Non-Steroidal Anti-Inflammatory Drug (NSAID) such as ibuprofen or naproxen can cause false positives for barbiturate immunoassays.
Read more: http://wiki.answers.com/Q/What_could_cause_a_false_positive_on_a_drug_test_for_barbiturates#ixzz286DyxPKp
Soma (carisoprodol) is metabolized as a barbiturate and I've also heard zoloft can, as well. I have also just read that NSAID's such as ibuprofen and naproxen can give a 0.4% false positive rate. Also; Glutethimide (Doriden), Phenytoin (Dilantin) give false positives for barbiturates.
http://www.askdocweb.com/falsepositives.html
here's a site that explains how you can get a false positive for barbiturates. You'll have to go through this long list though.
Best wishes finding your answers.