I am getting errors from Eclipse Indigo running on Windows 7 Ultimate. For each of the following items:
Android SDK content loader
Building workspace
Initial
check the Eclipse log (the intelligently named ".log" file in your workspace .metadata folder) and check for the complete stacktrace. In my case it was caused at method "org.eclipse.m2e.jdt.internal.MavenClasspathVariableInitializer.initialize(MavenClasspathVariableInitializer.java:30)" which lead to a never fixed "race condition during startup" bug. I would really recommend dumping Eclipse in favor of a more serious IDE; like IntelliJ or Netbeans. Using Eclipse means that you will invest 40-50% of your time trying to work around this kind of bugs, instead of being productive.