You will need to have admin priviledges on your computer! Try dragging the installer to your computer. Then double-click it.
If all that fails, get the Jum beta version. All you do is drag & drop the file from the opened dmg image wherever you desire.
http://www.mager.org/LimeWire/
I'd also recommend you update to the last OS 10.1.x which I think was 10.1.5 but i could be wrong.