# cvs -d:pserver:anonymous@cvs.berlios.de:/cvsroot/ser login
Logging in to :pserver:anonymous@cvs.berlios.de:2401/cvsroot/ser
CVS password:
# cvs -d:pserver:anonymous@cvs.berlios.de:/cvsroot/ser co sip_router
cvs [checkout aborted]: cannot stat /cvsroot/ser/locks: No such file or directory

It seems that cvs is broken, at least I was able to checkout another module.

# cvs -d:pserver:anonymous@cvs.berlios.de:/cvsroot/scrapbook co scrapbook
cvs checkout: Updating scrapbook
cvs checkout: Updating scrapbook/.settings
cvs checkout: Updating scrapbook/META-INF
cvs checkout: Updating scrapbook/WEB-INF
...