Are you by chance using a Linode? The Linode Debian 6 image had an issue with quotas… if you think that might be the issue, there’s a simple fix to that here:
/dev/sda6 on / type ext3 (rw,grpquota,errors=remount-ro,usrquota)
tmpfs on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
udev on /dev type tmpfs (rw,mode=0755)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=620)
/dev/sda1 on /boot type ext3 (rw)
The error now disappeared. May be it’s a caching issue after disabling the quota or may be because I ran quotaoff manually from cli. Thanks for your care, anyway.