Novice to rsgallery.

Trying to install RSgallery2 extension and every time i try to upload and install using either browse or from site, it hangs around for a while before trying to reload the index.php page which responds with '"browser" can't open page'. I've tried IE7, safari and different computers - no joy. When i check the extensions, it is not installed. Could be a permissions issue but i have no other ideas.

Now I know everyone else is loading it no problem so i need a  pointer. I'm hosting on siteground with Joomla 1.5 RC4 with legacy 1.0 enabled. I assume the graphics libraries are there and I can't see any other requirements.

TIA for any info. The demos look great so I hope it will work for me.