Do you have any tools installed which modify how Windows behaves, e.g. window layout tools, multi-monitor tools, or anything which adds buttons to the titlebars or similar?
e.g. In the past, someone found Winsplit Revolution seemed to caused this problem.
There's also a known conflict with Display Fusion where if DF is launched at startup after dopusrt.exe then DF's hooks never call back into dopusrt.exe's hooks, breaking desktop double-click unless you disable & re-enable it.