includes>class_core.php issue

[Eq4bits]

Not sure if this is where this should be but here goes.

I seem to have something really weird happening.
In the last 24 hours this has happened a couple of times too and I can't figure out why.
Somehow an extra 'return' is getting added to the end, all by itself, of my includes>class_core.php file.
I get a vbulletin error notice by email when a user gets the error message:

Database error in vBulletin :
mysql_connect(): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (11)
/home/*******/public_html/forums/includes/class_core.php on line 279

MySQL Error :
Error Number :
Date : Friday, June 16th 2006 @ 09:48:42 AM
Script : http://www.*****.***/forums/index.php
Referrer :
IP Address : **.***.***.***
Username :
Classname : vb_database

So at least I know by now to go to my file manager, and open that file to check it and everytime theres this 'extra return'.. I take it out (backspace it out), save the file and that fixes it. Then less than 24 hours later it happens again. How or what is happening to make this extra line keep getting added?
I'm the only one with access to the the files, so what gives?