VisualVM 1.2.1 has been released to fix compatibility issues with JDK 6 Update 17 (and newer) and several other problems:
- Issue 333: HeapWalker in VisualVM doesn't work with JDK 6 Update 17+
- Issue 327: Maximum value in Monitor charts is Integer.MAX_VALUE
- Issue 332: NPE in VisualVM-Sampler
See the Release Notes for more details. VisualVM 1.2.1 can be downloaded at https://visualvm.dev.java.net.