Welcome to the CentOS fora. Please see the recommended reading for new users linked in my signature.
That seems to be a pretty poor provider you are using. You should immediately update to the current release 5.8. 5.5 is seriously obsolete and has numerous known bugs and security issues that have been fixed in subsequent updates. Obsolete releases are not supported, nor is it advisable to be running them. See the CentOS 5.6 Release Notes
Section 4 for details on the recommended update procedure, and CentOS 5.8 Release Notes
for other information.
Edit: Just noted that you mentioned OpenVZ which means you are not really running CentOS at all. See:Other VoicesWhen CentOS Is Not CentOS