There is something about your project or setup that is not correct. I'm not exactly sure what the problem is that you are having. I need to know exactly what is working and what is not.

1. What kind of project is this? Spring? Groovy? Grails? Aspect? Roo?
2. Is this in all projects or just a single one?
3. Did this just start happening out of the blue, or is this with a new project or a new install?
4. Is open type working? Does it display all expected types? If not, which files are missing? Are they grouped in a certain area?
5. Is open resource working? Does it display all expected files?
6. Is content assist working? Does content assist display anything? Does it work in any files? Create a new, empty java project and create a new class. Does content assist work there?
7. Send your project to a colleague. Does your colleague have the same problem?

Answer these questions and we can begin to narrow down what is happening.