First things first, lets make sure your title is being defined. Open the page in question, right click and select 'view source', then do a find for <title> . If your title is there as it should be , then thats all good, if its not, or its a different title to what you expected you should get some support from the theme creator and/or all in one seo forum. Also make sure there is only one instance of <title> tag.
So if the title is there as expected, then check the Google cache of the page to see if its in that. Open the cached page in Google and right click view source again as above and search for the title. If there is a different title to what you have set is there you need to wait for Google to update its cache of your page. However if the correct title is there then we need to look at why the title isn't being displayed in the SERPS.
1. Google is displaying the company/web site name - The happens a lot when you are searching for you company/website name. Say your site is called 'Widgets Inc' and you use that to search for your site, Google will mostly replace the defined title with the company name.
2. Google is changing the title because you title is too long or there is more relevant content on the page - This happens quite often, if your title is too long to fit in the serps, or Google creates what it thinks its a better title than the one you have set using content from the page.
3. You have loads of duplicate titles - If you have loads of duplicate titles on your site (which you shouldn't) Google will often create titles its thinks are best for these pages.
To try and see what Google is really seeing as you title with out it replacing anything, try searching for you site using the search commands in google, and not keywords - Like this: site:mysite.com
