Starting in Firefox 44, Conkeror will give this error at startup:

1454083323678   addons.xpi      ERROR   startup failed: [Exception... "Component returned failure code:
0x80040111 (NS_ERROR_NOT_AVAILABLE) [nsIXPCComponents_Utils.isModuleLoaded]"  nsresult: "0x80040111
(NS_ERROR_NOT_AVAILABLE)"  location: "JS frame :: resource://gre/modules/addons/XPIProvider.jsm ::
XPI_startup :: line 2596"  data: no] Stack trace:
XPI_startup()@resource://gre/modules/addons/XPIProvider.jsm:2596 <
callProvider()@resource://gre/modules/AddonManager.jsm:221 <
_startProvider()@resource://gre/modules/AddonManager.jsm:828 <
AMI_startup()@resource://gre/modules/AddonManager.jsm:1006 <
AMP_startup()@resource://gre/modules/AddonManager.jsm:2758 <
AMC_observe()@resource://gre/components/addonManager.js:58

This will cause some addons to not load correctly, such as ABP. The cause of this error is this line:

http://mxr.mozilla.org/mozilla-release/source/toolkit/mozapps/extensions/internal/XPIProvider.jsm#2596

It appears to be the result of a restructuring of the Firefox Debugger placing it in a new location that
may not be accessible from firefox -app.