You likely being prevented from accessing Google fusion tables due to the Same Origin Policy.
Some ways to solve this is to proxy the request through your own server (running on the same domain as the page you are serving) or requesting the data in JSONP.
If you append the parameter jsonCallback=<callback name here>
to your Fusion Tables request, then you will get a JSONP response. For example, the request:
https://www.google.com/fusiontables/api/query?sql=SELECT+Address+FROM+914142+WHERE+IsCustomer+%3D+1&jsonCallback=foo
results in:
foo({"table":{"cols":["Address"],"rows":[["3400 California Street, Suite 302, San Francisco, CA 94118"],["1200 Pacific Avenue, San Francisco, CA 94109"],["340 10TH Street, San Francisco, CA 94103"],["One Embarcadero Center, Lobby Level, San Francisco, CA 94111"],["2230 Third Street, San Francisco, CA 94107"],["490 Post St, Suite 430, San Francisco, CA 94102"],["530 Bush St. Suite 101, San Francisco, CA 94108"],["114 Sansome Street, Suite 715, San Francisco, CA 94104"],["3012 Steiner Street Suite A, San Francisco, CA 94123"],["199 Fremont St # 105, San Francisco, CA 94105"],["2007 Irving St., San Francisco, CA 94122"],["450 Sutter Suite 2518, San Francisco, CA 94108"],["275 Gough Street, San Francisco, CA 94102"],["450 Sutter Street Suite 1225, San Francisco, CA 94108"],["2675 Geary Blvd., Ste 400, San Francisco, CA 94118"],["332 Pine St # 505, San Francisco, CA 94104"]]}})
This article from IBM should help get you understand JSONP and how to work with it: http://www.ibm.com/developerworks/library/wa-aj-jsonp1/