LinuxBabu ………..

There are many possible causes of this issue, however most relate to quotas being enabled on the filesystem itself.
Some ways to check the most common errors are:

Quotas enabled in the filesysem

By default, quoatas are enabled in the kernel on all SoftLayer Linux and FreeBSD kernels. If you’ve compiled/installed your own kernel, you’ll need to verify that quotas are enabled.

— FreeBSD systems will need to add “options QUOTA” to their kernel configuration and recompile. They will then need to add “enable_quotas=”YES”" to their /etc/rc.conf file.

— To enable quotas on a certain partition, one will need to modify the /etc/fstab file by adding usrquota (or grpquota if one desires the quota to pertain to an entire group rather than an individual user) to the options column (e.g. “LABEL=/home /home ext3 defaults,usrquota 0 0″).

— Once those entries are added, a reboot of the server should resolve the issue.

Run /scripts/fixquotas

Cpanel has it’s own tools to repair the quotas for it’s accounts. the command
#/scripts/fixquotas
run through ssh may resolve the issue.

Repquota

The command
#repquota -ua
will tell you if quotas are being reported for OS users at all.

Quotacheck

The command
#quotacheck -fv /home
will display the quotas for that filesystem, however the partition has to be unmounted first. It’s best to do this from Single User mode.