Look at potential causes for the problem
It's amazing how much you don't know about what you don't know. Therefore, in this phase, it's critical to get input from other people who notice the problem and who are affected by it. You will need to take a structured approach to finding out as much as you can about the problem.
Here are some ideas for how you might do this:
Once you have identified the problem and found out the causes of it it’s important to identify alternatives for approaches to resolve the problem. At this point, it's useful to keep others involved (unless you're facing a personal and/or employee performance problem). Brainstorm for solutions to the problem. Very simply put, brainstorming is collecting as many ideas as possible, and then screening them to find the best idea. It's critical when collecting the ideas to not pass any judgment on the ideas -- just write them down as you hear them.
To find out how to select the best approach for resolving problems have a look at Resolving Problems.