Incompatibility with Roboform add-on

[Morac]

If I install both HttpFox 0.8.8 and Roboform 0.7.8 (http://
www.roboform.com/), Firefox 4.0 for Windows basically breaks.

If I open a new window I get two title bars (the Firefox and Windows
one). Also the following appears in the error console:

Error: this.browsers[i] is undefined
Source file: chrome://browser/content/tabbrowser.xml
Line: 184
----------
Error: this.browsers[i] is undefined
Source file: chrome://browser/content/tabbrowser.xml
Line: 327
----------
Error: tabbrowser.browsers[ex] is undefined
Source file: resource://gre/components/nsSessionStore.js
Line: 2452
----------
Error: Component returned failure code: 0x80070057
(NS_ERROR_ILLEGAL_VALUE) [nsIObserverService.addObserver]
Source file: chrome://browser/content/browser.js
Line: 6748


If I disable either HttpFox or Roboform, everything is fine, but
nothing will work if both are installed. Note Roboform will also
attach itself (by default) to Firefox if the add-on is disabled. That
also causes the problem to occur.