In Eclipse, Alt+Shift+T is the default keybinding for the "Refactor" menu in Java. The Scala IDE now uses that binding for "Debug Scala JUnit Test" (Alt+Shift+T D) and "Run Scala JUnit Test" (Alt+Shift+T R).
This keyboard shortcut is in effect even when not in the scala perspective.

Scala's default keybinding should be set to something that doesn't conflict with built in eclipse shortcuts. Unfortunately, Alt+Shift+X T and Alt+Shift+D T are taken by the run/debug java junit test commands, but I think the scala ones (Debug/Run Scala JUnit Test) should be under the standard place, Alt+Shift+X and Alt+Shift+D.