We are currently unable to update plugins in our jenkins installation, because this exception occurs:

java.io.IOException: Failed to rename C:\Program Files (x86)\Jenkins\plugins\windows-slaves.jpi.tmp to C:\Program Files (x86)\Jenkins\plugins\windows-slaves.jpi
at hudson.model.UpdateCenter$InstallationJob.replace(UpdateCenter.java:1952)
at hudson.model.UpdateCenter$UpdateCenterConfiguration.install(UpdateCenter.java:1178)
at hudson.model.UpdateCenter$DownloadJob._run(UpdateCenter.java:1653)
at hudson.model.UpdateCenter$InstallationJob._run(UpdateCenter.java:1848)
at hudson.model.UpdateCenter$DownloadJob.run(UpdateCenter.java:1624)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at hudson.remoting.AtmostOneThreadExecutor$Worker.run(AtmostOneThreadExecutor.java:110)
at java.lang.Thread.run(Unknown Source)

It doesn't seem to affect all plugins, but it also happends for the JUnit plugin.