All our plugins require PHP 5.3 or later. If you try to enable them under PHP 5.2, one of the errors you might receive is Parse error: syntax error, unexpected T_PAAMAYIM_NEKUDOTAYIM, expecting ’)’, followed by a file name.
To solve the issue, you have to upgrade PHP to version 5.3 or higher, or ask your hosting provider to do so. It's a simple operation and should not require more than a couple of minutes. Of course, please make sure that you make a backup of your site(s) before proceeding. The upgrade to PHP 5.3 is fairly safe, but it's always better to keep backups before performing any important operation.