The “Already used” error that appears in Problem Desktops in View Administrator is a common problem that occurs with floating (non-persistent) desktops that you have assigned to refresh on log-off. This occurs for various reasons but all leave the desktop in an error state, which requires manual administrator intervention to resolve the issue.
Follow the following KB to permanently resolve the issue:
I set all of my floating pools to "pae-DirtyVMPolicy=2" by default.
