[Scottish] repairing a bad tar archive

[Tam McLaughlin]

Hi,
I have a bad tar file I created using smbtar which I need to restore from.

I can unzip the file but still get this error msg when I try and run 
tar tvf or xvf:

tar: This does not look like a tar archive
tar: Skipping to next header
tar: Error exit delayed from previous errors

This is what I get if I do 

file PC-392.Fri.full.tar
PC-392.Fri.full.tar: ASCII text

If I run strings on the file, I can see some of the readable data so it is not 
in tar format. Other backups have worked correctly for that particular day
using the same script/commands.

I tried using smbtar to restore from the archive but that also fails with:

checksums don't match 0 22394
abandoning restore, -1 from read tar header

Is there any way I can retrieve the data from the archive file?