Why can't I write a review for the apps I have bought?

New here. Recently got an iPad 2 and have purchased apps. I get pop ups to ask me to review and and I've also gone into the app store manually. I am able to highlight the stars but as soon as I type any words the submit button treys out so I can't send the review. All I can do is cancel. Really annoying. Any ideas? I have purchased directly from my iPad and I synch with pc.