I ran into this same problem using version 7.5.1 myself... however, I found the issue in a setting. To find it, go to:
Options > Other
click on the "Keys..." button
the 6th checkbox is "Shift key enables hotlinks"
With this option checked, you have to hold down the shift key in order for the mouse pointer to change to a hand over a URL and allow you to double-click and open it in a browser.
With this option UNchecked, you do not need to use the shift key and can simply double-click on URLs to open them in a browser.
I hope this information is helpful.
