Zend IDE mysteriously stopped debugging, firefox toolbar just would not start the debugger and always said Zend was not detected no matter what i done, turns out, it was listening on ipv6 ports

You can force Zend IDE into preferring ipv4 over ipv6 mode with

Open for editing the file Zend Studio installation directory/ZendStudio.ini and add the following line at the very end:

    -Djava.net.preferIPv4Stack=true

Than (re)start Zend Studio.

or disable your ipv6 stack with

sysctl -w net.ipv6.conf.all.disable_ipv6=1 

and double check you dont see 'tcp6' after you've restarted Zend IDE with

nine:/home/dgtlmoon/Zend/ZendStudio-7.2.0# netstat -platon | grep 10137
tcp        0      0 0.0.0.0:10137           0.0.0.0:*               LISTEN      3995/java        off (0.00/0/0)
tcp        0      0 127.0.0.1:10137         127.0.0.1:59532         ESTABLISHED 3995/java        off (0.00/0/0)
tcp        0      0 127.0.0.1:59532         127.0.0.1:10137         ESTABLISHED 4187/apache2     off (0.00/0/0)

As Zend IDE should always be listening on port 10137 (or whatever your debug port is)