Backup of file C:\WireframeSketcherStudio\jre\lib\rt.jar failed

Note to WireframeSketcher Studio Windows users. If you see an error like the one below you'll have to download the latest version manually. This error is caused by a JRE update which cannot be replaced due to an Eclipse bug.

An error occurred while uninstalling session context was:(profile=profile, phase=org.eclipse.equinox.internal.p2.engine.phases.Uninstall, operand=[R]com.wireframesketcher.studio.jre.win32_root.win32.win32.x86 1.6.0.22 --> null, action=org.eclipse.equinox.internal.p2.touchpoint.natives.actions.CleanupzipAction). Backup of file C:\WireframeSketcherStudio\jre\lib\rt.jar failed. File that was copied to backup could not be deleted: C:\WireframeSketcherStudio\jre\lib\rt.jar