When "couldn't write event header ..." is shown , the disk(nfsdesy) may be full.
In nfsdesy window, input "df" --> This command show the status of the disk.
Remove the older data after checking in cdcsv1 or jlclogin2.(The place of data in nfsdesy is  /disk1/DATA-GEM/cosm/ )

the place of data in jlccdcsv1 is /home/daq/data/mpitpc/2007/gem/cosm/