A month after purchasing my Nexus 7, I found that it won't start. In frustration I left it and decided to go to the shop to seek assistance. In the meantime I looked for help in the forums but did not find anything convincing. At about 5pm I went to the shop. The shop assistant turned the switch on and the Nexus 7 started working. He advised me not to charge it overnight or for  long hours as the battery gets jammed when it is over charged. I found that as I left it on for a few hours, it discharged some power and therefore it was ready to turn on. Since then I've been using it for another month without any further problems. So I hope this story might help other people who are having trouble  turning their nexus on.
Mirh.