It may happen that a task can't be started or continued due to an absolute interruption. For instance, the internet connection went down for some reason. When that happens, should I start the timer and count the time I try to solve this problem as part of the task or should the problem be solved before using the timer?
David Allen (GTD) published this video a while back as a way to deal with Interruptions http://www.youtube.com/watch?v=MLp0PYsQTjU I suggest you apply this technique and see if it works for you.
If something prevents you from progressing on a certain task leave it and move on. Trying to resolve an issue is a task and should also be timed.
If you want to be strict, if your internet went down and you have to diverge from your task, you should void your pomodoro or start the new one "unplanned".
Although you should think why you are using pomodoro technique in the first place.
If you using this technique to say that you using it and you starting pomodoro just to have pleasure that you doing so, maybe you can manage to clear yourself.... But by using this technique you can achieve something else. You can learn how to organise your workplace, your plans and an environment in the first place. Maybe if your internet disrupts you, it is time to ask "could you do something in the future to plan better?" of course it would depend upon your task but not many of them are in 100% achieved by using the internet.
By using pomodoro technique you can learn to be better orginised not to be better pomodoro's ticker. The technique is about planning, not about ticking boxes. If your task needs some amount of time to accomplish you can finish it only by giving your time only to the task, not to fixing the internet.
Of course you need some fun in your life as well so don't be to strict.