95% of the reason for denial of a clearance for HPSP students is bad credit. The other 5% are citizenship and other integrity issues (simply lying on the application for the clearance).
In reality, the process is that you apply for the clearance. Once you come up as a risk, the security office will attempt you contact you to answer for the credit issue, and see what steps you are taking to rectify the situation. They may suspend your clearance, or deny it all together. However, while this is playing out, you are in school, HPSP is paying for your tuition and stipend, books and equipment. For the Army, the HPSP office normally isn't notified of your lack of clearance until the second ADT. Why so long? It can take 16-18 months for a good clearance to be issued. The first ADT is either BOLC or school within 9 months of the start of the scholarship. Further, students ignore the Security Office and the Security Office is not authorized to "share" personal information with any other entity. So the HPSP office will not find out until it's time for the second ADT - two years down the road.
What happens next? Either the student is able to prove that he is taking steps to rectify the bad debt, or the clearance is denied. Once the clearance is denied, you are not eligible for the scholarship and now owe the Army all the money spent on your behalf. Think about that for a minute. You owe the world so much money and you are in default and can't be in the Army, then on top of that, you now owe the Army for two years of school, stipend, 20K bonus, books, and equipment. And, because you have bad credit, you can't get loans for the last two years of school so you have to quit. And, by-the-way the Government debt cannot be discharged through bankruptcy and must be paid back within 10 years.
Best advice is to pay your debts. Some effort, as much as you can afford each month CONSISTENTLY. Keep up your payment plan. The security office wants to see a serious effort is being made over the course of a year or more...