Non uso firefox , ma :
1)setta per bene la pagina iniziale
2)usa adwcleaner come spiegato -->
qui postando il report dopo la funzione "pulisci".
Verifica se si riapre.
Ho usato ADWCleaner e finora nn si è ripresentato il problema..
Questo è il report dopo la funzione "pulisci"
# AdwCleaner v2.306 - Logfile creato il 03/01/2015 alle 13:43:13
# Aggiornamento 19/07/2013 by Xplode
# Sistema Operativo : Windows 7 Home Premium Service Pack 1 (64 bits)
# Utente : Roberto - ROBERTO-PC
# Modalità Avvio : Modalità Normale
# Eseguito da : C:\Users\Roberto\Desktop\programmi utilità pc\ANTIVIRUS MALWARE\AdwCleaner.exe
# Opzioni [Cerca]
***** [Servizi] *****
***** [File / Cartelle] *****
Cartella Trovato : C:\Program Files (x86)\Common Files\AVG Secure Search
***** [Registro] *****
***** [Browser Internet] *****
-\\ Internet Explorer v10.0.9200.17183
[OK] Registro Pulito.
-\\ Mozilla Firefox v34.0.5 (x86 it)
File : C:\Users\Roberto\AppData\Roaming\Mozilla\Firefox\Profiles\a7i26nur.default-1369131537386\prefs.js
[OK] File Pulito.
-\\ Google Chrome v35.0.1916.114
File : C:\Users\Roberto\AppData\Local\Google\Chrome\User Data\Default\Preferences
[OK] File Pulito.
*************************
AdwCleaner[R10].txt - [2115 octets] - [21/05/2014 11:58:02]
AdwCleaner[R11].txt - [2728 octets] - [26/05/2014 23:02:28]
AdwCleaner[R12].txt - [2298 octets] - [27/05/2014 00:40:55]
AdwCleaner[R13].txt - [2420 octets] - [27/05/2014 13:31:54]
AdwCleaner[R14].txt - [2542 octets] - [03/06/2014 13:54:18]
AdwCleaner[R15].txt - [2664 octets] - [06/06/2014 22:50:37]
AdwCleaner[R16].txt - [2786 octets] - [07/06/2014 16:12:03]
AdwCleaner[R17].txt - [3457 octets] - [13/06/2014 10:20:25]
AdwCleaner[R18].txt - [3028 octets] - [01/07/2014 13:50:42]
AdwCleaner[R19].txt - [3150 octets] - [03/07/2014 00:00:41]
AdwCleaner[R1].txt - [27928 octets] - [04/08/2013 13:33:57]
AdwCleaner[R20].txt - [3272 octets] - [17/07/2014 07:03:10]
AdwCleaner[R22].txt - [3520 octets] - [30/07/2014 22:24:35]
AdwCleaner[R23].txt - [3459 octets] - [26/08/2014 09:02:04]
AdwCleaner[R24].txt - [3581 octets] - [03/09/2014 18:50:11]
AdwCleaner[R25].txt - [3744 octets] - [29/11/2014 18:01:22]
AdwCleaner[R26].txt - [3827 octets] - [03/01/2015 10:54:55]
AdwCleaner[R27].txt - [2006 octets] - [03/01/2015 13:43:13]
AdwCleaner[R2].txt - [1376 octets] - [10/10/2013 11:58:48]
AdwCleaner[R3].txt - [1920 octets] - [06/12/2013 14:04:47]
AdwCleaner[R4].txt - [1980 octets] - [06/12/2013 14:05:15]
AdwCleaner[R5].txt - [1616 octets] - [25/02/2014 23:40:42]
AdwCleaner[R6].txt - [1735 octets] - [03/03/2014 11:23:58]
AdwCleaner[R7].txt - [1812 octets] - [24/04/2014 08:49:52]
AdwCleaner[R8].txt - [1872 octets] - [24/04/2014 08:51:08]
AdwCleaner[R9].txt - [1994 octets] - [13/05/2014 09:00:56]
AdwCleaner[S10].txt - [2365 octets] - [27/05/2014 00:41:23]
AdwCleaner[S11].txt - [2487 octets] - [27/05/2014 13:32:40]
AdwCleaner[S12].txt - [2609 octets] - [03/06/2014 13:54:49]
AdwCleaner[S13].txt - [2731 octets] - [06/06/2014 22:51:28]
AdwCleaner[S14].txt - [2853 octets] - [07/06/2014 16:19:54]
AdwCleaner[S15].txt - [3443 octets] - [13/06/2014 10:21:21]
AdwCleaner[S16].txt - [3095 octets] - [01/07/2014 13:51:09]
AdwCleaner[S17].txt - [3217 octets] - [03/07/2014 00:01:45]
AdwCleaner[S18].txt - [3339 octets] - [17/07/2014 07:04:27]
AdwCleaner[S1].txt - [28698 octets] - [04/08/2013 13:34:37]
AdwCleaner[S20].txt - [3526 octets] - [26/08/2014 09:03:03]
AdwCleaner[S21].txt - [3648 octets] - [03/09/2014 18:50:41]
AdwCleaner[S22].txt - [3813 octets] - [29/11/2014 18:02:00]
AdwCleaner[S23].txt - [3894 octets] - [03/01/2015 10:57:23]
AdwCleaner[S2].txt - [391 octets] - [10/10/2013 11:59:51]
AdwCleaner[S3].txt - [1490 octets] - [10/10/2013 12:01:23]
AdwCleaner[S4].txt - [2060 octets] - [06/12/2013 14:06:03]
AdwCleaner[S5].txt - [391 octets] - [25/02/2014 23:41:15]
AdwCleaner[S6].txt - [1803 octets] - [03/03/2014 11:24:48]
AdwCleaner[S7].txt - [1938 octets] - [24/04/2014 08:51:54]
AdwCleaner[S8].txt - [2060 octets] - [13/05/2014 09:01:45]
AdwCleaner[S9].txt - [2644 octets] - [26/05/2014 23:03:23]
########## EOF - C:\AdwCleaner[R27].txt - [3879 octets] ##########