Why such occurs at neobux.com?

I have been working with neobux.com a PTC site since November, 2011. It is a legit but poor earning site. High valued ads are rarely available here. During this period of more than 1 month, I got on 2 or 3 occasions, one high valued ad of $.005 each among the low priced ads of $.001 that means a total number of 2 or 3 of such high valued ads in the total period of more than 1 month. I gladly clicked on those ads. On each occasion, the ad started loading, I was directed to wait until loading was complete like in other cases and the click was validated. But unfortunately what I saw in all the cases. When I was eagerly waiting to see the message that an amount of $.005 had been credited to my account, I saw an ‘error’ message and the site cited some cause which in all such cases remained the same for the failure and asked me to refresh the page for further attempt. I followed the direction but in no case I could achieve success. Thus I wasted time and energy for loading the ad and viewing it but was deprived of my genuine earning on the ground of ‘error’. Have anyone any such experience with neobux? Is it really a technical fault on the part of neobux or is it a deliberate cheating on the part of neobux?