os installer crashed

the OS installer was running then suddenly it crashed.i don't know what the installer was actually trying to do when it crashed.This is happening again and again.restarting the installation is not solving the problem.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubiquity 2.21.63
ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
Uname: Linux 4.4.0-21-generic x86_64
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
CasperVersion: 1.376
Date: Fri May 27 12:59:06 2016
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz.efi file=/cdrom/preseed/ubuntu.seed cdrom-detect/try-usb=true persistent noprompt floppy.allowed_drive_mask=0 ignore_uuid boot=casper only-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
ProcEnviron:
 LANGUAGE=en_IN
 PATH=(custom, no user)
 LANG=en_IN
 SHELL=/bin/bash
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)