There is no restriction to the number times you can download or even install Photoshop. The license restriction applies to how many computers you then launch and use the application on. You shouldn't have a problem with downloading. I would suggest clearing you browser cache and cookies, or use a different browser.
Alternatively you can try downloading from the direct download links available at : http://prodesigntools.com/all-adobe-cs5-direct-download-links.html
But make sure you follow the important steps mentioned on the page before initiating the download.