seems there has been a wrong timestamp on repomd.xml

Now it's working again:

Code:
host:~ # zypper ref
Repository 'SUSE-Linux-Enterprise-Server-11-SP3 11.3.3-1.138' is up to date.
Repository 'SUSE-Linux-Enterprise-Software-Development-Kit-11-SP3 11.3.3-1.69' is up to date.
Repository 'SLES11-SP3-Extension-Store' is up to date.
Repository 'SLES11-SP3-Pool' is up to date.
Repository 'SLES11-SP3-Updates' is up to date.
All repositories have been refreshed.
host:~ #
I heard Novell is preparing a permanent fix for that.

HTH, Thomas