Sometimes our OSB Eclipse projects get corrupted, or sometimes you need to create new workspace from existing source code (from project source code control).
Here are steps I use:
I'll assume your entire OSB source is under a folder call "c:/osb".
0. back up your osb folder (if you used it for an existing workspace), e.g. rename it osb.bak
1. create new folder "c:/osb"
2. check out your source files under "c:/osb", e.g. ("my config proj", "my proj1", "my proj2")
or copy your backed project files if you backed them in step 0
3. fire up eclipse, switch to OSB pespective, and create a new workspace under "c:/osb"
4. select "file", "import", "general", then "existing projects into workspace"
5. pick your "c:/osb" folder, check and uncheck the projects you want
6. import them
7. it may whine about your .svn, or .vss files, you can ignore them, or you can google it up, i believe there is way to mask off those warnings in Eclipse preference, i just don't remember how
8. if you happen to see one of the projects showing error saying it doesn't have an associated OSB configuration project, just drag that project in Eclipse "project explorer" panel, and drop it into your OSB configuration project.
hope that takes care of everything.