I agree that honesty is best but also use this opportunity to show that you're poised and professional.   In any job you need to be able to answer difficult questions without being negative or unprofessional.

Make sure to emphasize that while you find your current position satisfying and enjoyed that opportunity, the financial struggles they're experiencing mean that you can no longer afford to work there. 

I'm sure the company you're interviewing at is looking at a number of qualified candidates and all things being equal the situation you're in might give you the edge over another candidate.

Good luck!