Mysql admin and plesk

Hi,

I have some problems with read/write permission of *.MYD files (this file is auto generate to data folders of mysql) , my application show error message about "can't read/write *.MYD files" but if I do "skip-grant-tables" and update new password of admin everything work fine, can you suggest me how to prevent that it happens again in the future because I already did it last time and the error happen yesterday.

My application run on vps with .net technology and mysql.
Plesk version 9.0.


Thanks in advance,
Book