Not enough informations. Low priced niche? no optimizations? ads which are not content relevant show up?
Your niche could be one of the poor paying category or there may be too many invalid clicks for which you will not be paid any dollar
To me this is common. How you get your share is from how much advertiser are willing to pay for certain keywords. It also depends on which advertiser that will be displayed on your pages. Obviously they're ways on how you could work around this, but still it's not 100% guaranteed. Only Google knows exactly how, who, when to show the highly paid advertiser on any pages.
Looks like your Niche is not high paying one, but you still are making more than what I make, that is, I get $0.03 per click all the time. I suggest you try to increase the amount of traffic as Traffic = $$$ and if possible, improve the CTR.
Your niche is most likely very poor. But that doesn't have to mean you can't make money. By combining banner/link exchanges and affiliate programs you can make money by placing ads on sites with better niches. See my blog for more info.