Thread:Project:Support desk/wiki is hanging after a while, port 80 not available

Mediawiki 1.20.2 / PHP 5.4.7 / MySQL 5.0.51 on our apache we have a intranet and an internal WIKI running. A few times a day the intranet en the wiki is hanging. We have to stop and start the apache (2.4). Investigation shows that at those moments the port 80 is not available. We did some testing. Seems like when we remove WIKI from the apache and only run intranet, there is no problem. when we add wiki back to the apache the problem occurs again. Any idea what the problem may be?