I had GF 1.4 installed on my website ( http://www.stayanight.co.za ) and it worked fine. I've been testing 1.5 on a test site ( http://www.jbayclassifieds.co.za ) and working fine.
The problem I have is that I uninstalled (Deleted all files) 1.4 on http://www.stayanight.co.za and then installed 1.5. It is working fine but when I try using the "Enable Page Conditional Logic" on a new form it only gives me a blank screen.
You can test and see it here:
Working copy (v1.5 installed from start) - http://jbayclassifieds.co.za/wp-content/plugins/gravityforms/preview.php?id=3
Not Working (had v1.4 and now installed v1.5) - http://www.stayanight.co.za/wp-content/plugins/gravityforms/preview.php?id=2
Both forms were created exactly the same way