Most likely you have an access_log on a site somewhere that is over the 2 gig limit Manual. Technically, this limit is in the statistics program, not Webalizer, but since statistics call webalizer it shows up as a symptom.
First you'll need to find the oversize file. The following should help you with that (log in as root and adjust the path as necessary for your Plesk installation):
CODE
ls -alh /home/httpd/vhosts/*/statistics/logs/access* | sort -n +4
Once you sort out which file or files are over 2 gigabytes you have a choice. If the stats aren't important to you, you can simply delete the oversized files and run webalizer manually. If the stats are important, you'll want to split the oversized file and run statistics a few times until you have things caught back up.
To run the statistics manually is
CODE
/usr/local/psa/admin/sbin/statistics
Pay attention for errrors being reported as it's running.
Once you have everything cleaned up the best way to prevent this sort of thing from happening in the future is to enable Log Rotation for all domains on the server. Your best bet it to have log rotation triggered by the filesize, rather than a date. You can do this right in Plesk. You'll also probably want to set it up so that your rotated log files are compressed since this will take these files down to around 5% of the size of the uncompressed version.
There are lots of posts over on the
Plesk forums detailing different things you can do, depending upon what exactly is stopping webalizer in its tracks.