Entering into PhD program after having dropped out of bachelor's When I was 23, I quit my computer science undergraduate studies at USC with only one semester worth of units left and a low (less than 3.0) GPA due to personal reasons.  I just turned 30 and have rekindled a desire to pursue research in computational neuroscience.  Is there any realistic hope of eventually getting into a PhD program and pursuing a career in academia, or is it too much of a long shot given my personal circumstances and the job market?  

Basically, what I want to know is, if I were to finish my BS, kick ass in a master's program (applied mathematics), and have great GRE scores, would that overcome my abysmal undergraduate record and gap in years away from school?

The biggest obstacle in my view is getting into a terminal master's program with my undergraduate record.  If I were to get into a 1-year terminal master's program in mathematics at a sub-par university and do great, would I have a chance at a higher ranked university for my PhD?
The odds of a career in academia are long in general, and certainly your situation is going to make the odds even longer.  

That said, people tend to only look at your most recent degree.  It seems pretty likely that if you got into a masters program and did very well there, you'd have a good shot at getting into a solid Ph.D. program.  But you'd actually have to do very well in the masters program (probably "best in several years" level).  Furthermore, even once you get into a solid Ph.D. program the odds are against your getting a job in academia.