backup on tc fails: too many open files

hi, we use tc as our backup system and run automatized from a "netgear" ready-nas-file-server a backup on our time machine. works all fine - except with one backup script where tc complains "too many open files". (the share which is backuped on tc contains a lot of small files - it is a svn-repository).
here a part of the log file with the last successfull and the first failure file
where //repository" is the mount point of the tc on the file server:
/_3.0/db/revs/1905'
`./svn/repos/_3.0/db/revs/3095' -> `/job 015//repository/svn/repos/3.0/db/revs/3095'
cp: cannot create regular file `/job 015//repository/svn/repos/3.0/db/revs/3095': Too many open files

regards,
philipp