I have a problem with my solver for excel?

I have excel 2008 for a Mac which does not come with solver so I had to download it from frontline. It isn't working well though. Whenever I select the cells I want to input it does not register them so I have to type them in manually. Also once I have all my parameters entered into the solver it doesn't give me any results, it says there is an error and I should check if the constraints are entered correctly even though they are. Could I have installed it wrongly or something?