Eclipse 3.8 missing project list

Question

Eclipse

Without a declaration of war and other messages in Eclipse 3.8, the list of all projects disappeared.
Only in the log:

!ENTRY org.eclipse.core.resources 4 567 2014-05-05 22:54:14.302
!MESSAGE Could not read metadata for '/home/pavelk/Projects/.metadata/.plugins/org.eclipse.core.resources/.root/.indexes/properties.index'. Unexpected version: -47.

!ENTRY org.eclipse.ui.workbench 4 2 2014-05-05 22:54:16.599
!MESSAGE Problems occurred when invoking code from plug-in: "org.eclipse.ui.workbench".
!STACK 1

The projects themselves are complete.
All plugins and other installations are in place, as are the projects themselves.
How can this problem be solved, and what should be added to the backup copy so that this does not happen again?
Preferably without re-importing projects.
OS - Ubuntu 13.10.

Answer 1

I understood about backup - .metadata It's a
pity, I thought the project settings in the project folders are saved. After import, there are no build and launch settings =(