Log in loops again for a particular user [duplicate]

Question

I was logging into my ubuntu machine till last night. Today I had an error unknown group ID error for the group I was in and also the UID. But I had no errors till the last night. I lost my sudo access too. I can ssh into my machine and account but when I log in to through GUI I get a blank screen and Then I added the group ID to /etc/group. I can't login after editing them. karthik.singaravelan is my username here. Here are the /etc/group and /etc/passwd files

root:x:0:karthik.singaravelan
daemon:x:1:
bin:x:2:
sys:x:3:
adm:x:4:aspire
tty:x:5:
disk:x:6:
lp:x:7:
mail:x:8:
news:x:9:
uucp:x:10:
man:x:12:
proxy:x:13:
kmem:x:15:
dialout:x:20:
fax:x:21:
voice:x:22:
cdrom:x:24:aspire
floppy:x:25:
tape:x:26:
sudo:x:27:aspire
audio:x:29:pulse
dip:x:30:aspire
www-data:x:33:
backup:x:34:
operator:x:37:
list:x:38:
irc:x:39:
src:x:40:
gnats:x:41:
shadow:x:42:
utmp:x:43:
video:x:44:
sasl:x:45:
plugdev:x:46:aspire
staff:x:50:
games:x:60:
users:x:100:
nogroup:x:65534:
libuuid:x:101:
crontab:x:102:
syslog:x:103:
fuse:x:104:
messagebus:x:105:
bluetooth:x:106:
scanner:x:107:
colord:x:108:
lpadmin:x:109:aspire
ssl-cert:x:110:
lightdm:x:111:
nopasswdlogin:x:112:
netdev:x:113:
whoopsie:x:114:
mlocate:x:115:
ssh:x:116:
avahi-autoipd:x:117:
avahi:x:118:
pulse:x:119:
pulse-access:x:120:
utempter:x:121:
rtkit:x:122:
saned:x:123:
aspire:x:1000:
sambashare:x:124:aspire
mysql:x:125:
rabbitmq:x:126:
mongodb:x:127:mongodb
memcache:x:128:
tomcat6:x:129:
karthik.singaravelan:x:1001:

/etc/passwd

root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/bin/sh
bin:x:2:2:bin:/bin:/bin/sh
sys:x:3:3:sys:/dev:/bin/sh
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/bin/sh
man:x:6:12:man:/var/cache/man:/bin/sh
lp:x:7:7:lp:/var/spool/lpd:/bin/sh
mail:x:8:8:mail:/var/mail:/bin/sh
news:x:9:9:news:/var/spool/news:/bin/sh
uucp:x:10:10:uucp:/var/spool/uucp:/bin/sh
proxy:x:13:13:proxy:/bin:/bin/sh
www-data:x:33:33:www-data:/var/www:/bin/sh
backup:x:34:34:backup:/var/backups:/bin/sh
list:x:38:38:Mailing List Manager:/var/list:/bin/sh
irc:x:39:39:ircd:/var/run/ircd:/bin/sh
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/bin/sh
nobody:x:65534:65534:nobody:/nonexistent:/bin/sh
libuuid:x:100:101::/var/lib/libuuid:/bin/sh
syslog:x:101:103::/home/syslog:/bin/false
messagebus:x:102:105::/var/run/dbus:/bin/false
colord:x:103:108:colord colour management daemon,,,:/var/lib/colord:/bin/false
lightdm:x:104:111:Light Display Manager:/var/lib/lightdm:/bin/false
whoopsie:x:105:114::/nonexistent:/bin/false
avahi-autoipd:x:106:117:Avahi autoip daemon,,,:/var/lib/avahi-autoipd:/bin/false
avahi:x:107:118:Avahi mDNS daemon,,,:/var/run/avahi-daemon:/bin/false
usbmux:x:108:46:usbmux daemon,,,:/home/usbmux:/bin/false
kernoops:x:109:65534:Kernel Oops Tracking Daemon,,,:/:/bin/false
pulse:x:110:119:PulseAudio daemon,,,:/var/run/pulse:/bin/false
rtkit:x:111:122:RealtimeKit,,,:/proc:/bin/false
speech-dispatcher:x:112:29:Speech Dispatcher,,,:/var/run/speech-dispatcher:/bin/sh
hplip:x:113:7:HPLIP system user,,,:/var/run/hplip:/bin/false
saned:x:114:123::/home/saned:/bin/false
aspire:x:1000:1000:aspire,,,:/home/aspire:/bin/bash
sshd:x:115:65534::/var/run/sshd:/usr/sbin/nologin
mysql:x:116:125:MySQL Server,,,:/nonexistent:/bin/false
rabbitmq:x:117:126:RabbitMQ messaging server,,,:/var/lib/rabbitmq:/bin/false
mongodb:x:118:65534::/home/mongodb:/bin/false
memcache:x:119:128:Memcached,,,:/nonexistent:/bin/false
tomcat6:x:120:129::/usr/share/tomcat6:/bin/false
karthik.singaravelan:x:1001:1001::/home/karthik.singaravelan:/bin/sh

output of id karthik.singaravelan

uid=1001(karthik.singaravelan) gid=1001(karthik.singaravelan) groups=1001(karthik.singaravelan),0(root),1352140539(power^users),1352554700(linux),1352139265(domain^users)

Is there any error with the config files that lets me not to log in? Other users can log in from my machine and I can log in from others machines. Whenever I press enter to login it goes black and returns to the screen. Kindly help me on this issue.

Answer 1

The Xauthority file was pointing to a group that doesn't exist and thus stuck at the login. I SSHed into my machine and removed the .Xauthority file, logging out and logging in creates a new Xauthority file with relevant permissions and thus logs into the account. Thanks @muru a lot for helping me on this issue. Also setting the Xauthority file to another existing group will solve this issue.