Upgrade from version 7.0.2 to version 7.1.1 page blank

Hello to all. I’m trying to do the upgrade from version 7.0.2 to version 7.1.1. The first step checks the system after a few minutes of processing gives me a blank page. How can I fix?
PHP Version 5.3.3
Mysql 5.1.7.1 versionn
Cache / custom / modules / themes / date / upload chmod 775

No one can give me an answer? thanks

I solved it. I looked at the file upgradeWizard.log and I found a folder, not suitecrm, loaded on the server that did not have the permissions 775. Changed permissions to that folder everything worked. I hope this can be useful to others.
Thanks, see you soon

Well done achlive, but what was the folder?

Hello techeccentric, the folder is one of those tests that install hosting services. It is not a folder suitecrm. I found out the name of the file folder leggendo upgradeWizard.log. Try looking at what it says your upgradeWizard.log. See you soon