Also, what is the likelihood that a power supply issue would be the cause of the direction problems that I outlined in prior posts?

I would say it is almost certain that the bad power supply is the cause of the direction problems 

Tweakie.

That sounds expensive for a psu ??

What size - voltage and current is it meant to be ?

The psu came installed in a prewired control box.  I priced the individual components that were recommended on various forums, and it was roughly the same to wire myself in-comparison to a prewired control box.  Also, I lack the electronic expertise to tackle such a project.  The following link outlines the components in my setup.   http://www.automationtechnologiesinc.com/products-page/g0704-kit/3-axis-cnc-stepper-control-box  I am questioning the overall quality of the psu, since it has lasted only two years with minimal usage.  

So its just the 5v psu thats failed?

I should think just about any 5v switch-mode psu would work, the BOB only draws minimal current and a 2A unit here in the UK would be about £10

I have not checked all the details of your unit though so please take my advice carefully