Eclipse Error: Cannot determine URI for /project-path/

Question

I'm running Eclipse Luna on Ubuntu 12.0.4 in VirtualBox with a Windows 8 host and every once in a while, I will boot up Ubuntu and open up Eclipse to find this:

My projects should be listed in the package explorer but it's all empty and whenever I try to import the project again, it says no projects are found.

At this point, I usually go to my workspace folder and delete the .lock file and rebuild the workspace but is there an alternative to this? This error happens every ~5 times I reopen Eclipse and it has become very annoying. Any help will be appreciated!

EDIT: Okay I just tried deleting the .lock file in the .metadata folder in my workspace and I'm still getting the same error. Any suggestions?

EDIT 2: While closing my currently open tabs, I got this error. The projects that were open were Maven projects if that makes a difference.

Solution

so I am a little late for the party, but I fixed that on reimporting my projects.

Under File->Import.. you choose General->Import existing Projects into workspace. On the next page you set your workspace directory as the root directory for importing, which will give you a warning like "Some projects already exist in workspace". Ignore this and click finish. After that all my projects where back in my workspace.

Good luck