By default the Mozilla Firefox (and other) browsers will not allow local files to be accessed from a web based application.
Only if you changed some FF settings, a site could access your local files (in this case the subscriptions or directly patterns.ini)
see an example:
http://www.meccanoindex.co.uk/Firefox.php?id=1315550748
ABP "forgets" about filter settings depending on vsited site
Re: ABP "forgets" about filter settings depending on vsited site
see here: forum/viewtopic.php?f=1&t=28742
an issue similar with yours ==> it was a nasty addon in firefox, so check again your addons and remove one by one
an issue similar with yours ==> it was a nasty addon in firefox, so check again your addons and remove one by one