Any time I open a browser window, including when Firefox first starts up, I get a lot of the following errors in the error console:
Error: Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIURI.host]
Source file: chrome://adblockplus/content/policy.js
Line: 387
This is with Firefox 3.5.1 and AdBlockPlus 1.1 under Windows XP SP3.
Errors when opening new windows
Not sure how you got there, probably some other extension required to see this issue. Either way, fixed: http://hg.mozdev.org/adblockplus/rev/b2506d685bb0. A development build with this fix will be available in four hours under devbuilds/adblockplus/. I would appreciate it if you tried that development build to confirm that the issue is solved.