Firefox is slow and unresponsive when Norton Toolbar 2015 is active

Problem: Since I installed the 2015 beta software (Norton Security -formerly: Norton Internet Security), Firefox is very slow and unresponsive

Example: opening a new tab takes 5 - 7 second, and during this time Firefox is totally unresponsive, and doesn't do anything.

If I disable the Norton Toolbar version: 2015.0.0.39, the problem doesn't appear, and firefox is very fast again, new tabs open under 1 second.

 

Internet Explorer 11 is unaffected.

 

NS: 22.0.0.67

OS: Windows 7 SP1 64-bit

Firefox: Latest RTM - version 30