WordPress Won't Upload Themes

I have been having problems with WordPress, every time I try to upload a theme, it won’t upload. Every time it goes to the “Uploading Theme” page after you press upload, and then after that it says “Unpacking the package” and never finishes and keeps like that in-till I “X” out of the page, and then I look at my themes and it isn’t there. If there is anyway any one can help? Thanks!