it seems you've tried to run the plugin under php 4. There are certain syntactic restrictions on how to program object-oriented in php 4, where in php 5 one can shorten the code quite a bit. It's just a matter of a simple edit to fix this particular error, but there will be further errors like this on many other lines.
So the only way this can be fixed immediately is to switch to a more recent version of php, which is always a good idea.
If you run your website on a shared webhosting provider, there might be an option to use php 5 by default somewhere in your admin area.
If you don't know how to check you version of php just create a empty textfile named
phpinfo.php and put this single line of code into it:
<?php phpinfo() ?>
Then upload it and view this file in your browser. This will reveal a huge insight in the php configuration of your web hosting, including the php version number.
If you've got further problems regarding the plugin a link to this file will help me a lot tackling the problem.
ps. I appreciate every single vote on my plugin - once you get it to function, of course.