Plugin Installation Issue … could not create directory

Hi,

I’ve my own domain, hosting and have manually installed the wordpress successfully. Everything was working fine, however, when am trying to install plugin am getting the error… installation failed as could not create the directory.

After some research I’ve also tried to change the permissions of the folder wp-content/upload to 777 however immediately after changing the permissions when i check … i could see that it has again switched over back to 755… it doesnt rest on 777. Kindly help me asap. How do i install the plugin. (ive downloaded the latest version of wordpress from ww.wp.xz.cn… am not sure about the version)

Thanks,
Sunny