The problem you're experiencing is that this website is using a re-direction service. What that means is that the thumbnails don't point directly to the imagevenue page. Instead, it first visits the re-direction page, then it visits the imagevenue page.
http://www.hentairules.net/gal/re.php?redir=http://img124.imagevenue.com/img.php?image=23230_inside_www.hentairules.net_01_02_123_155lo.jpg
Observe that the first part of the URL is:
http://www.hentairules.net/gal/re.php?redir=
These have to be removed before you can use IHG on these galleries. The solution is to use my "Redirection Remover" script for grease monkey. Visit the page below:
http://imagehost-grabber.com/greasemonkeyscripts.htmlRead the directions on installing grease monkey. Once grease monkey is installed, go back to the page and find "Redirection Remover" and click on the link. It should prompt you to install it for grease monkey. Once installed, go back to the gallery you posted, right click on the grease monkey icon (located at the bottom right corner of the firefox window), click "Manage User Scripts", find "Redirection Remover" in the list on the left side of the window, and hit "Add" in the "Included Pages" area. The default value that comes up in the pop-up box will work fine. Once that is done, you will have to refresh the gallery page. Make sure that the links have been adjusted to remove the redirection url. To do this, hover the mouse over one of the thumbnails and look at the status bar. It should display the link. It should look something like:
http://img124.imagevenue.com/img.php?image=23230_inside_www.hentairules.net_01_02_123_155lo.jpg
Let me know if you need any further assistance with this.
Matt