There's a common misconception that some kind of direct link exists between credit problems and security clearances. This is not the case.
Bad credit is not a "terminal illness" for security clearances, but it is a symptom - a possible indication - that a more serious problem lies beneath the surface, and must be looked into. For example: if the reason for the bad credit is a gambling addiction, then the gambling addiction (NOT the bad credit) could be a reason to deny security access. Or if the financial predicament puts an individual in a position where they might do something irrational, then that potential for irrational behavior (again, NOT the bad credit) could be a reason to deny security access.
So having bad credit basically means you're going to have to answer two follow-on questions: "How/why did it get this way?", and "How will you deal with this?". It's the answers to those two questions that will determine how much (or how little) the company can place its trust in you.
- Greg