Thanks a lot for providing the thread dumps. I looked at them and it seems like there is some issue with the new e4 UI platform going on. Can you download and install the STS 3.1.0 distribution that is based on Eclipse 3.8 to see if the problem goes away using that version? It is available from the STS download page and contains exactly the same feature set (just uses the older UI implementation from Eclipse). My hope is that it solves the issue you are seeing.