Unable to update/install various plugins

[rec]

Hi all,

I notice failures in plugin updates/installs recently along these lines:

hudson.util.IOException2: Failed to download from http://updates.jenkins-ci.org/download/plugins/m2release/0.14.0/m2release.hpi
	at hudson.model.UpdateCenter$UpdateCenterConfiguration.download(UpdateCenter.java:794)
	at hudson.model.UpdateCenter$DownloadJob._run(UpdateCenter.java:1138)
	at hudson.model.UpdateCenter$InstallationJob._run(UpdateCenter.java:1298)
	at hudson.model.UpdateCenter$DownloadJob.run(UpdateCenter.java:1116)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
	at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
	at java.util.concurrent.FutureTask.run(FutureTask.java:138)
	at hudson.remoting.AtmostOneThreadExecutor$Worker.run(AtmostOneThreadExecutor.java:104)
	at java.lang.Thread.run(Thread.java:662)
Caused by: java.io.IOException: Server returned HTTP response code: 504 for URL: http://mirrors.jenkins-ci.org/plugins/m2release/0.14.0/m2release.hpi
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
	at sun.net.www.protocol.http.HttpURLConnection$6.run(HttpURLConnection.java:1491)
	at java.security.AccessController.doPrivileged(Native Method)
	at sun.net.www.protocol.http.HttpURLConnection.getChainedException(HttpURLConnection.java:1485)
	at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1139)
	at hudson.model.UpdateCenter$UpdateCenterConfiguration.download(UpdateCenter.java:764)
	... 8 more
Caused by: java.io.IOException: Server returned HTTP response code: 504 for URL: http://mirrors.jenkins-ci.org/plugins/m2release/0.14.0/m2release.hpi
	at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1436)
	at sun.net.www.protocol.http.HttpURLConnection.getHeaderField(HttpURLConnection.java:2308)
	at java.net.URLConnection.getHeaderFieldInt(URLConnection.java:579)
	at java.net.URLConnection.getContentLength(URLConnection.java:474)
	at hudson.model.UpdateCenter$UpdateCenterConfiguration.download(UpdateCenter.java:763)
	... 8 more

Is there a known problem and/or workaround? Google didn't enlighten me and scanning through this list briefly also not.

Cheers,

-- Richard