What do you do when you get assigned a project that is just way too hard to do:
SO users, I would love realistic answers here. This is a real world situation and I am trying to figure out my response to my boss tomorrow on how to approach him delicately.
I just wanted to add an update to my note here. The app in question that my boss is targeting is a "NING like" web app. My hesitation is mostly being the only person being assigned to it for such a complicated app in such a short time period.
This is a situation that everyone has to deal with on a regular basis simply due to the nature of work. (Typically, if you know everything you need to know to complete a job, you've already completed the job and don't need to do it again. :) )
Be honest with your boss about your anxiety. Your manager needs to understand your assessment of the project's risk profile. Odds are good that you'll be doing it anyway. That's OK! This is your chance to shine! :)
Break the problem down into tasks you understand and tasks you don't understand, then start tackling issues one at a time. I, personally, like to alternate between easy tasks and hard tasks. Completing easy tasks helps me feel like I'm making real progress on a gut level, which is important for my personal motivation. Completing hard tasks addresses potential problem areas earlier in the schedule. This mitigates the tail-end risk of the project by evaluating unknowns earlier, rather than letting them fester and explode when you've got 2 days left and no more planning/wiggle room. It also helps your stress level because you know you've gotten the ball rolling on the project's scary bits. Remember-- your unknown areas are where you don't understand the problem domain, so that's where the real risk of schedule/budget slips lie. You need to mitigate those risks early and often. Get the ball rolling with colleagues that you can consult to learn how to do these things.
The one month goal is probably a target. I don't believe it's reasonable to expect person A to realistically estimate person B's scheduled completion of a task in the general case. To track your progress against the target, set up milestones, none longer than 16 hours/2 days, and track your completion rate against them. This goes hand-in-hand with your list of easy/hard tasks.
The simple fact is that, sometimes, you'll just get dumped in over your head. In that case, you may have to make the best of an overwhelming situation. My very first task at my first job out of college was to design a reliable, transaction-oriented, peer-to-peer n-way server synchronization system for high-volume, high-rate data. I told my boss up front that I did not have the expertise for this, and at the time I didn't have enough experience to understand that I needed to push back on the requirements. (In retrospect, given the political environment, I don't know if pushing back on the requirements would really have helped anyway). That was simply a case of a poorly managed project that took about 18 months to ultimately collapse under its own weight. I still leveraged the opportunity to learn a lot and take some knowledge about the way my particular organization worked, though, and that can be very valuable no matter what. :)
Good luck! :)
Edit after question update
Ok, if I understand your update correctly, we're definitely in #4 territory here. There's nothing realistic about creating a competitor for Ning in one man-month. I assumed in my prior answer that you were dealing with someone who had a base understanding of software development. Based on that:
Ask your boss to clarify the requirements more. Perhaps (cross your fingers!) you simply misunderstood what you were being asked to do, or the scope of the project. Always assume competence until absolutely proven otherwise for social reasons. Maybe you were only being asked to come up with an overall design and some very simple proof of concept?
If your boss is truly this out of touch with reality, put together a sensible, 15-minute back-of-the-envelope estimate with him/her on a whiteboard or a shared piece of paper. It shouldn't be hard at all to blow all kinds of holes in this one month to completion. Perhaps your boss thinks you'll be able to reuse some internal code that you're not aware of? This will bring any faulty assumptions your manager is making re: project scope to light.
If your boss is absolutely unreasonable (this doesn't happen often, but it occasionally does-- perhaps the company needs a killer app by the end of the month to sell to avoid going under), prep your resume for an intra- or extra-organizational move (depending on how big the place you work is). Unrealistic expectations on that order can be a sign of organizational desperation or malfunction, and your position may simply not exist 3 months from now.