IMHO, the underlying cause is the culmination of centuries of decline of the Muslim world versus the West, beginning in the 18th Century and continuing to the Turkish defeat in WWI and later carving up of most of the Middle East into British and French colonies. Fascist groups, some emphasizing Islam, others more secular, formed to resist colonization and to fill the power vacuum left by the Turkish retreat. The Arabs hadn't governed themselves for four centuries by this time.
This is why OBL dreams of reestablishing the Caliphate, which symbolizes this decline. The Turks took the title of Caliph, head both of the faith and government, from the Arabs and then the last Turkish Caliph was deposed after WWI. There hasn't been a Caliph since.
The solution, IMHO, is not just to fight the islamo-fascists, but even more important is to get the Arab world plugged into the global community and economy so they will feel part of the modern world and not estranged from it.