cpio: memory exhausted

[Thomas McLaughlin]

This is probably not the place for my query, but I have exhausted other 
avenues and would be glad of some help.

I can't work out what's going on with my nightly cpio backup.
If I do:

  cd /
  find . -print | cpio -ocv 2>$OUT > /dev/st0

and read back the contents using

  cpio -itv </dev/st0

we get a partial list of files and then:
cpio: memory exhausted

I have tried using dd to get some data from the tape and then

  cpio -itv <dd.out

I still get the cpio error after less than 1 minute. I read back ~ 300Mb so
it has not reached the end of the archive file.
I am using Mandrake 7.1 kernel 2.2.15-4mdk with an adaptec scsi card and 
20Gb DAT drive.
It does not look like a memory problem as I still have free memory and can
vi a 13Mb file. 

I have been trying to narrow down this problem by using cpio to backup 
a small number of files, both to disk and tape but not got this error yet.
However I have came accross another strange problem with cpio in that
I can't get a list of files backup from std err. e.g.

  find . -depth -print | cpio -ocv 2>../backup.log  >../backup.cpio
  cat ../backup.log
  1129 blocks

but i should get a list of files in backup.log, as I do with the same cmd 
running on a Red Hat 6.0 2.2.5-22 server with same tape device.

Any ideas? I had thought that there could have been a hardware error with  
the scsi card  but this seemed unlikely as I can create smaller
backups without any errors and cant find any errors in the log files.