What is the world's hardest programming problem that hasn't been solved?

There are lots of programming problems that have yet to be solved. Here a few related to the IT discipline itself:

• Declarative language: The dream of the declarative language is to tell the computer “What you want done” instead of telling it “How to do it”. there is a lot work to be done there.
• Analysis, Design and Programming Methodologies: All current methodologies help you document the design; But you have to create the design in your head first. It would be really cool to have one that actually helps you do the design.
• Knowledge Engineering: Computers still do not “understand”. With neural networks they can be trained to give certain responses, there is still no way for a computer to “learn” i.e. gain knowledge.
• Massively Parallel Applications: Current massive parallel systems are designed to do floating point calculations. We could really use a paradigm for business to use the massively parallel systems of the near future.

Here a couple of technology related:

• Task Scheduling: Modern CPU’s with multi-cores, multi pipeline (hyper-thread), and multi-level caches require a new scheduling algorithm which takes into consideration the state of the caches, pipelines and cores… The current algorithms just use the state of the cores, which can lead to Cache Thrashing.
• Browser Application Development: A decent solution to programming applications in browsers. The current one is simply not good.