Hello,
I have installed the add on, enabled, unticked the disable script option but it does not catch any java script errors. I am on windows XP sp2 using IE6.0.Below is the information from About dialogue of js companion

Companion.JS BHO loaded : OK
JS Debugger Thread not running : PROBLEM
JS debugger version : OLD
JS Debugger not connected : LIMITATION - OLD debugger is not working in protected mode
Internet Explorer Version : 6.0.2900.218
Protected Mode : OFF

I have installed debug bar also I have visual studio 2008 installed on the system, before installing js companion visual studio debugger use to kick in for javascript errors now neither vs debugger nor js companion works, I am in a kind of tricky situation to identify js errors.
Appreciate your quick reply.

Thanks,
San