I think the design itself looks professional. No complaints about it.
My question for you is, where is your traffic coming from? SEO? PPC? Word of mouth? This might have some effect on your conversions. Also, depending on where you are getting your traffic from may affect how you design your landing pages so they are tuned for conversions.
For example, if you are using Pay-Per-Click advertising, you`d want to remove the top navigation so as not to distract the user. You`d want the page solely tuned for conversions and nothing else, since you are paying for every click.
Another thing you should consider is what is the norm conversion rate for your industry, given your channels of online advertising? Is your conversion rate above, below or at norm? If it below, then this would suggest there is something you need to change. But if it is at or above norm, your probably aren`t doing anything "wrong". But that also doesn`t mean you shouldn`t try to continually improve.
Finally, the single best way to know for sure if your copy is optimized for conversions is to test variations of the copy and web page. Sure, we can give you our honest opinions, but nothing will give you more accurate suggestions than actual user interaction with your site. Go to Google Website Optimizer, and set up some Website A/B testing to see which versions convert more.
Best of luck!
Motivation for Entrepreneurs