Hi,
1. Check the file ownership and permissions of the .SAR file beforehand list them here.
2. Also when you extract it do you use the SAPCAR located in one of the exe directories i.e. /usr/sap/<SID>/DVEBMGS<NO>/exe/SAPCAR -xvf FILE.SAR or did you copy the SAPCAR file to your /usr/sap/trans dir?
3. If you say that is only the one file, have you perhaps re-downloaded that file and then try to re-extract it?
4. Which version of SAPCAR are you using? Usually recommended as always with SAP to use the latest version.
As for more information you can add -e option to output details of extraction to an std_out file
Kind Regards,