Islam and its raiders/pirates basically destroyed trade in the Med. But to claim that this in and of itself destroyed all trade across Europe seems a bit of a stretch. Riverborne and land routes were still available, if a lot more expensive.
During the period in question, the Vikings were ravaging north and west Europe, the Saracens were attacking from the South, and the Magyars were attacking from the East.
Each of these groups penetrated so far into the Continent that it brings up the possibility of their actually bumping into each other. In fact, it's probable, since we know some of the Viking raids penetrated into the Med.
Magyar raids penetrated into central Spain, western France, and southern Italy. They really got around. http://en.wikipedia.org/wiki/File:Kalandozasok.jpg
IOW, the decline of trade and civilization was not due solely or even necessarily to Islamic aggression.
I have to point out Islam was the worst of these groups and they controlled the seas raiding at will.
When Rome controlled the seas and roads they were relatively safe for trade.