Serious cvs tag/rtag issues Please help

[Pranab Panda (pkpanda)]

Hi All

In last couple of days our cvs server has gone done few times,
Checkin and checkout work fine, but
since this afternoon I see errors with cvs tag and rtag commands.
They both fail with following error
cvs [rtag aborted]: could not open lock file
`/auto/cvsroot/repository/Files/,file12,': File exists

I am clueless how to fix this.
Please help if know whats the issue
this is very critical!

NOTE: cvs --version 
Concurrent Versions System (CVS) 1.11.2 (client/server)
On Linux 2.4.21-27.0.1.ELsmp #1 SMP Mon Dec 20 18:47:45 EST 2004 i686
i686 i386 GNU/Linux

Thanks in advance
pranab