This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
Here is what I would do: I'd start with a fresh install of Eclipse and try to import the project. If that doesn't work, the issues is with one of the files in the projects (based on the error messages, I'd look at the timestamps on the files). If that works, I would add in the plugins one at a time, each time starting with a new workspace and recreating the project. That should at least tell you which plugin is causing the problem.