Could not find Library.apk!
I managed to restructure my application pretty nicely so that, except for a few methods in a derived Activity class, everything is in a Library Project.
It works beautifully, except that Eclipse's Console (not LogCat!) issues the following error message:
[2011-06-13 19:54:08 - MyLibrary] Could not find MyLibrary.apk!
I cleaned both projects (library and application), restarted Eclipse, re-built the projects, but this weird error message persists.
What does this error message mean? (especially in light that everything seems to be running OK)
How do I get rid of it?
UPDATE: I tried removing the project then re-importing it per the suggestion below. It didn't help. I then found this thread that helped me realize that I had <uses-library> in the application's AndroidManifest.xml referring to MyLibrary. I deleted it, cleaned the project and rebuilt. The problem persists.
I am now suspecting this is "real problem", e.g. misconfiguration of some paths or something else on my part. What could it be?
Answer
I found the source of the problem!
It turns out that "with the new library feature, you don't specify the Android projects you depend on in the Java Build Path section of the Properties. You do it in the Android section of the Properties".
So all I had to do is go the Application Project's Properties, hit the Projects tab, select my own library project and click the Remove button. That's it. No more problem.
In Eclipse Java EE select the project Properties, then select Project References, then check the FacebookSDK (see screen capture) 
Thanks to Lance Nanek!