I'm not going to vouch one way or another because SEO is an inexact science... and many things passed as SEO practices truly do nothing to improve your search engine ranking.  Please keep in mind that e107 powers your actual site and its content, although it is bridged with SMF.

This is going a good bit beyond the scope of what we offer with the charter membership, but I will give you some tips from experiences with the situation and what myself and another noticed in terms of indexing and things that i can see may be a factor (but also may not be).  These are in no particular order of importance.

1.) Content is king.  Expand your content and make it easily visible and accessible.

2.) 301 Redirect -- while 301 redirects are good in terms of relocating individual articles or pieces of information -- your entire site is under a 302 redirect and your entire forum is under a 301 redirect.  While google, for example, is capable of following redirects, it generally is best to avoid needing to redirect unless absolutely necessary. I suspect this is a provision of your cms, e107.

3.) Backlinks: your forum only has only 2 external backlinks to it. Whilst your main site only has 350.  This is other sites linking back to you.  If you're not aware, google's search rankings are heavily affected by backlinks.  You should seek to affiliate with other sites in your niche.  The more links, the higher the page rank, the more Spiders will index.

4.) Meta keywords -- your meta keywords are set as the smf default.  While keywords lately are largely ignored, having keywords that are relevant to what people are searching for AND related to your content CAN help.  Some statistics softwares such as awstats compile a list of links based on its data collections that *may* be of some use, but this must be installed at the server level so there is no guarantee your host offers this.

5.) Your redirected forum link is the third folder down from the root.  Again, while google and most spiders can filter down into the lower folders provided available links, folders farther down in the hierarchy are generally considered lesser related 
to your main site content and may not be as strongly indexed.

6.) Fine tune robots.txt - make sure that your robots.txt is blocking off any and all irrelevant or duplicated content (content with multiple links -- redirected or otherwise).  Google only indexes so much -- make sure it indexes what you want.

7.) Generate/submit a sitemap - this helps google find your site sections.

8.) HTML Validation -- the validator at w3.org reports 503 html errors in your site -- this will give google a hard time in crawling your site and in seperating your content from its presentational HTML.

9.) Some links have double double quotes on them ie: <a href=""http://www.karulures.com/"" -- you should only have one set of double quotes.  This likely contributes to your HTML validation problems.

In all, i think your problem is both with software as well as the actual logistics of your site, but I do not feel nor am I convinced at this point that SMF is the cause for your SEO problems.

I hope that offers some insight into things.  It is by no means meant to be a plan or a list of things to accomplish.