When Firefox closes, filter subscription disappears

[graymattr]

When I close Firefox, the filter subscription disappears and doesn't work the next time I open Firefox. Then I have to download and add the subscription again. This just started last week after Adblock Plus worked perfectly on this computer for over six months. I've also tried creating a backup of the subscription and restoring from the backup after exiting and restarting Firefox but the subscription still isn't there. The subscription isn't affected in Chrome on this same computer, it stays as expected.

I'm using Firefox 36.0.1 and Adblock Plus 2.6.5 on a Windows 7 pc.

[mapx]

If you already tried disabling the other addons and keep only ABP and still happens:

could happen when the firefox profile was corrupted
try resetting FF and reinstall ABP (and the other addons)

[graymattr]

I was ready to reset Firefox but decided to remove Adblock Plus, exit Firefox, then reinstalled Adblock Plus. I've exited and started a few times and it has worked fine and I'm happy with it.

Should have thought of this sooner.

[Endeeo]

I tried Google Chrome on my now rather old PC(with Windows XP). As before it seems incompatible with other progs so I uninstalled it and tried to go back as before. Unfortunately now Ad Block Plus disappears whenver I exit Firefox. I've 'Refreshed' numerous times but each time I re-download Adblock Plus I get the message "Adblock Plus could not be installed because Firefox cannot modify needed file".I've even uninstalled Firefox and re-downloaded v 36.0.4(X86en-GB). All to no avail. Sometimes Ad block will load but then disappear as soon as I exit Firefox and I have to start all over again! Can anyone tell me what I have to do to make Adblock 'stay'? ('Easylist' filters referred to in several Forum threads is ticked).
I HATE GOOGLE CHROME!

[mapx]

Did you reset firefox ? (as indicated here for your issue https://support.mozilla.org/en-US/questions/974165 )
Did you try to test ABP without installing other addons ?
Are you testing using an admin account ?
Disable also - if any - web shields of your antivirus and re-test