There are some problems, which I've become aware of over time, which tend to take a long time to explain to the layman, because they involve layers of abstraction, that are hard problems. But it's not the abstraction that makes them hard, its programmers and power users and "experts" who really keep things from getting fixed.
Why? Because we feel the issue isn't important, or has already been addressed adequately.
This list will grow, but here's a few to start from.
1. Computer Security - I've talked about this one at length, but the basic gist of this is that the idea of trusting application code, or anything outside of the microkernel of the OS, is insanely stupid. Yet all the Linux fanboys are convinced they don't have anything to worry about. The Network security folks see it all as either dumb users, lazy admins, or bad programmers. Nobody sees the broken security model that got obsolete once Unix left the classroom in the 1970s.
2. Metadata as part of the operating system's job. - There was a good set of blog posts by the person who headed up the Microsoft efforts to integrate metadata into the OS, the last attempt being WinFS. As with problems in this list, it takes a lot of time just to explain the problem. Linux doesn't do it, Windows failed to do it, and we're all the poorer as a result. You should be able to manage and transport metadata with a file, across systems, and just have it work.
3. I haven't found this one yet, and it will take someone an hour just to explain it to me, should they convince me to listen that long... and I'll have an ah-ha moment.... and add it here.
What are your Hard problems in computing? Doc Searls probably would put VRM vs CRM in here, as an example.