Even though I am a MSCS with lots of IT experience, I had to uninstall the latest version of ZA (12.0.104) as it made my home's Internet Explorer to practically freeze (Yahoo!, Google, MSN, and even the own ZA websites not accessible!) - while crippling Firefox 25 (which could still run some sites but not Yahoo!). No tuning or reconfiguring worked! Uninstalled it and re-installed Rel. 11.0.768, then everything went back to normal. Running a 64-bit Windows 7 Pro desktop. This is very weird!