Airbus has had much success with the A332 - its the surprise "star" of the A330-A340 series since it is the right size, offers good range and is very versatile; the A330 did not attract many orders until first the A332 arrived and then the improved A330-300X. I am sure that Boeing has noticed Airbus' success in the important 200-250 pax long haul market, a market previously owned by Boeing.
As a Boeing fan, I find it disappointing that the 764 has, to date, been of little interest to most airlines. Its a good plane, no doubt, but its market niche is quite small trying to fill the void between the 763 and 772.........I always thought that Boeing might have been better off building a 771 instead of the 764, but that is just my opinion. Also, the 764 has had very bad timing, coming on to the market just as many of the major airlines bought additional 763s, as the world economy started to falter, and of course, 9/11.
I think that the 764 will have some success in a few years time, Boeing has had many products that struggled and then gained popularity a few years after introduction. The 764 is an ideal replacement for AA's A300s, for example, in a few years time when AA is considering renewing its fleet;DL and CO may follow up with additional orders when traffic numbers improve, etc. Also as mentioned above, in a few years time, airlines will only start to think about replacing early build 762s and 763s, and only then will the 764 attract more interest.
Also, remember that when airline traffic starts growing again and when the economy is back on track, airlines (especially those in the USA) will need larger medium haul airliners to operate between their hubs and major destinations. Airports will become too crowded to simply keep adding frequency, and aircraft like the 764 (and the 753) will increase in popularity.