After canceling a previous build with Ctrl-C Gradle wasn't able to start another build anymore.

It turned out that a lock file (~/.gradle/caches/artifacts/org.slf4j/slf4j-api/wharfdata-1.6.2.kryo.lck in my case) was still lingering in the cache directory, causing an infinite hang.
After deleting said file, everything worked fine again.

The attached file is the stacktrace at the time of the hang.