There are two places in the 46xxsettings.txt files where you can find this.
The first is:
################ SCREEN SAVER SETTINGS ###################
##
## Idle Time Before the Screen Saver is activated (minutes)
## Number of minutes without phone activity to wait
## before the screen saver is activated. A value of 0 means
## the screen saver is never activated.
## The default is 240 minutes.
##
## SET SCREENSAVERON 240
Possibly the ## in front of the set screensaveron are not there in your file. They need to be there to rem out that line.
The second place is set specific and look like the following:
############################################################
#
# SETTINGS4625
#
############################################################
##
## This section contains the phone model specific settings
## for the 4625 telephone.
##
## The WMLHOME setting is used to enable and
## administer the 'Web' Application.
##
## The WMLIDLEURI setting acts as an idle screen when the
## phone has been idle (see WMLIDLETIME value). By default
## this URL is NULL ("") and this screen is not
## activated.
##
## NOTE:
## Avaya hosts a web site for IP Phones.
## The WMLHOME and WMLIDLEURI parameters are set up
## to point your IP telephones to this hosted site.
## To enable access to this site, remove the "## "
## from the SET WMLHOME ... and SET WMLIDLEURI ... lines.
## To change the web site that your phones point to,
## replace the provided URL in the SET WMLHOME .. and
## SET WMLIDELURI ...lines with the URL of your site.
##
## SET WMLHOME
## SET WMLIDLEURI
Once again you will want to rem out the Set wmlidleuri line.
Just a guess.