An SUA-based application becomes unresponsive, and the Psxss.exe process uses 100 percent of CPU time on a Windows Vista-based or a Windows Server 2008-based computer
You are running an application that is based on Subsystem for UNIX-based Applications (SUA) on a Windows Vista-based or a Windows Server 2008-based computer. However, the application becomes unresponsive. Additionally, Task Manager shows that the Psxss.exe process consumes 100 percent of CPU time. This problem typically occurs when you start or stop the application.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB967484.