Inclusion Criteria:

- Pathologically documented NSCLC

- Locally advanced (Stage III) or metastatic (Stage IV) NSCLC

- Only one prior anti-tumor treatment regimen in the non-curative setting (i.e.,
2nd-line therapy)

- Only one prior anti-tumor treatment regimen in the curative setting

- Progressive disease following the previous anti-tumor treatment regimen

- Measurable disease by RECIST criteria

- Brain metastasis must be stable and well-controlled

- ECOG performance score 0-2

- All anti-tumor therapy discontinued at least 3 weeks prior to study entry

- All adverse events from prior treatment are resolved or stable

- Adequate hematologic, renal, and hepatic function

- Females must not be pregnant

- Willing to take adequate measures to prevent pregnancy

- Life expectancy of at least 3 months

- Able to complete the Quality of Life questionnaire

- Voluntarily signed informed consent

Exclusion Criteria:

- Greater than Grade 1 neurological findings

- Allergy to sulfa medications

- Previous treatment with ABT-751 or pemetrexed

- Receipt of more than one investigational agent for NSCLC

- Significant weight loss (>10%) within 6 weeks of study entry

- Glucose-6-phosphate dehydrogenase deficiency or porphyria

- Significant systemic disease that would adversely affect participation

- Class 3-4 New York Heart Association classification status

- Other cancers except in situ carcinoma of the cervix, basal or squamous cell skin
cancer, or any other cancer considered adequately treated and cured by the
investigator