viper2k5

hi guys im new to the forum and was after some help im building my online store with cubecart v6 and everything was going well until ive tried to add paypal and shipping to the page i have downloaded and installed all the plug ins via the market place but when i try to go into any of the options to edit/manage the plug in i just keep getting a white page and nothing loads i have tried this on 3 machines and the same thing keeps happening, anybody have any ideas why this happens and how i can sort this thanks in advance Lee