Firstly, which version of PCLinuxOS are you running there?
If it is one of the 2011.06 KDE, 20011.07 LXDE series, you should open up Synaptic - the package handler.
After putting in your root password, press the Reload button in the top left corner. After a short time, press Mark all Upgrades.
Press Apply > Apply and leave the machine to update totally.
Then, under PC (the button at the left end of the panel), choose LO Manager. It will then use the latest version of LO Manager to install Libre Office into your machine.
To install LibreOffice by direct downloading an rpm can be done but runs the risk of not finding the required dependencies > a package that will fail. Therefore, since I returned to using PCLinuxOS exclusively, I have made a policy of not installing by any other method than through Synaptic. Thus, I have found my success rate has improved considerably.
Over the past few days, when using Firefox 6.0, I kept getting little messages saying that Firefox 6.0.1 was ready for download. I ignored these invitations and, last evening, I did an update through Synaptic. There, Firefox 6.0.1 (and Thunderbird 6.0.1) were detected and updated.
The approach that I (and others) advocate will surely cut down on the need for reinstallation of the entire PCLinuxOS distro.