Be honest. If you quit, then there are many reasons to quit and settle for a different job. If you were fired or laid off, be honest about it, they will be fine.
"My previous IT position had several disadvantages. The company did not invest enough in IT to maintain their equipment, and so rather than pursuing opportunities to bring technology to the workers and enable them to be more productive, I spent most of my time fighting fires and keeping the systems running. I could see from this decision, and others they were making, that they were not interested in moving the company, as a whole, forward to meet the challenges of tomorrow, and provide their customers with better services - they were simply extracting as much money from the company and employees as they could. I chose to leave prior to finding a better IT position due to the work schedule, which precluded a reasonable job search. Further, I wanted a great fit with a new company, rather than simply hiring with the best available opening. It turns out that I learned a lot working within a warehouse which I can apply to my IT discipline, on top of being able to spend a reasonable amount of time finding the best fit for me and my future employer without worrying about financial constraints."
You can turn any "disadvantage" into an advantage. The only problem with the above statement is that since you spent so much time fighting fires you might not be up on the latest technologies. That should be dealt with in the technical portion of the interview, though, and you can indicate how you still pursued and learned such technologies, even in such a bad environment.
