Error when merging posts

[masterme]

I want to merge 2 posts of the same user, nothing special, small messages.
But when I click to merge, I get this message:

[B]Fatal error[/B]: Allowed memory size of 8388608 bytes exhausted (tried to allocate 44 bytes) in [B]/home/xxxxxx/domains/mydomain.ext/public_html/forum/includes/adminfunctions.php[/B] on line [B]3021[/B]

The line 3021 is below:

 build_datastore('usergroupcache', serialize($vbulletin->usergroupcache), 1);

When I do a refresh, the two messages are merged, so it succeeds anyway.
But this error keeps popping up each time I do a merging, what is this?

[Colin F]

Your memory limit in PHP is extremely low. Try adding this line to your config.php file, right under the <?php line:

ini_set('memory_limit', 32 * 1024 * 1024);

[masterme]

Mmm, when I do that, I get this error:

Warning: ini_set() has been disabled for security reasons in (showing the line I added)

[Steve Machol]

Unfortunately your only other hope is to ask your host to increase the php.ini 'memory_limit' setting. I recommend 32M. They may have to restart Apache after making this change.