restoring backup

Hi, we are trying to restore a back up but get the following error. Please advise.
Thank you
Ivan
*************
Please wait extracting backup file
Feb 26, 2008 12:40:16 PM com.adventnet.j2ee.deployment.service.internal.JarExtractor extract
INFO: Extraction for /root/backup_servicedesk_7011_fullbackup_02_25_2008_16_32.data to /root/AdventNet/ME/ServiceDesk/bin/..
java.io.EOFException: Unexpected end of ZLIB input stream
at java.util.zip.InflaterInputStream.fill(Unknown Source)
at java.util.zip.InflaterInputStream.read(Unknown Source)
at java.util.zip.ZipInputStream.read(Unknown Source)
at com.adventnet.j2ee.deployment.service.internal.JarExtractor.extract(JarExtractor.java:130)
at com.adventnet.j2ee.deployment.service.internal.JarExtractor.extract(JarExtractor.java:79)
at com.adventnet.servicedesk.tools.RestoreSDBackup.deCompressData(RestoreSDBackup.java:667)
at com.adventnet.servicedesk.tools.RestoreSDBackup.restoreDatabase(RestoreSDBackup.java:105)
at com.adventnet.servicedesk.tools.RestoreSDBackup.main(RestoreSDBackup.java:84)
at com.adventnet.servicedesk.tools.RestoreDialog.main(RestoreDialog.java:317)
Unable to restore database : Unexpected end of ZLIB input stream