You've gotta be very patient here. It will fail quite a few times on this part, just have to be persistant.
Some things you can try to have better odds at success:
Direct connection to PS3 & modem/router via Ethernet Cable (If possible)
if not, have it as close to it as you can get it for best possible connection.
Also, the web pages where these tools are, such as the DUMPER, make bookmarks of these for quick access, as the PS3 browser is not the best for this, but you have no choice. Make sure you have cleared your browser's cache, cookies, history, all that after you've made the appropriate bookmarks.
Set the DUMPER page as the page that will load up on browser start.
Once you do this, close the browser, start it back up and go directly to the dumper page.
Even with doing this you may still fail. Try it a few times, close browser, and retry it again until you get success.
I know how aggrevating this part can be xD