wordpress stripping trailing / from WordPress Address (URL)

My wordpress installation is served from a subdiectory living in a site that is served from a subdirectory on a shared host.

The main site uses a rewrite rule in iis to serve the site from the subdirectory, though I don’t think that is relevent, as wordpress is using .htacess for premalinks reather than an iis rule.

The blog should be served from http://www.theartoflovingcatsanddogs.com/blog/, which works fine. However, google has indexed “http://www.theartoflovingcatsanddogs.com/blog“(without the trailing slash), which for some reason redirects to:
http://www.theartoflovingcatsanddogs.com/site_theartoflovingcatsanddogs_com/blog/

And it gives a error from wordpress rather than the main page:

Not Found

Apologies, but the page you requested could not be found. Perhaps searching will help.

I tried going into the wordpress settings and adding the slash but it gets stripped of. This is the only place I can think of that the lack of the slash is coming from as the main site has the slash on all the links.

I’m not sure what the solution is. Maybe modify the .htaccess file used by the wordpress directory? I would not know how to do that but maybe someone on here can help me? Is there another solution?