Password file gets corrupted

[Sumith Ail]

Hello List,
We are facing a wierd problem with Qmail + Vpopmail 4.9.8-1 using CDB
authentication on RH 6.2. All the virtual domains are under the clients
own home dir to support unix disk quota restriction.
So, when the Unix system disk quota gets filled up, the vpasswd file
becomes 0 bytes and the users cannot authenticate to fetch their
mails. This has happened twice and only when the Disk quota gets filled
up.
Would appreciate any insights in this regard.

B Rgds
Sumith