[Fordrus]

Report, report, report. Who are you delivering the final product to? Email that person, tell that person during stand-up, "I discovered issue X in my project today, this pushes back my deadline by Y hours/days/weeks/months/millennia." You don't HAVE to manage the entire fallout, necessarily, right away, but if you start raising alarm bells early, you can harness your team to assist in adapting! :)

The other thing? CUT. Can't have feature completed by next week? What are the parameters? Could you do a mock-up or a skeleton of it and have it serve the immediate, urgent purpose, while potentially still moving you towards final feature nirvana? Better phrased: you've hit a snag, you can't deliver what you said, on the deadline that you said- especially if you fear that manager you'll be reporting to, tell him/her what you CAN still deliver on that timetable. "What CAN you deliver, then?" is almost certainly on someone in your chain of command's mind, desperately begging for an answer! :)