There are many problems with the A380, only a few of them are technical:
1) Too big. It requires major upgrades to Runways and Aircraft handling facilities not to mention gate areas. With the slump in air travel after 9/11 many airlines and airports are not willing to pay this price and won't be anytime soon. As a result, no US based airline has placed an order for the A380 and likely never will.
2) Airbus is arguing internally about where certain parts should be build and assembled. Since they are a consortium owned my several European governments (France, Germany, Spain and the UK IIRC) this issue tends to fall along national boundaries and national pride is an issue. Internal management changes and disputes, accusations of severe mismanagement, fraud and pressures from the high powered European Workers Unions (demanding better wages, shorter work weeks, more vacation and a socialist revolution) are all working against the success of the A380.
3) Fuel efficiency. 4 Engines burn more fuel that 2. All 4 of Boeings best offerings get better gas mileage (757, 767, 777 and the soon to be 787). With prices creeping up at the pump, the A380 is not seen as an optimal buy for many airlines.
4) Airline have been configuring hubs much more in the last few years. You fly people on lots of flights between a few cities and then shuffle them around. The A380 holds too many people for it's own good. At a time when airlines are having a problem filling seats between hubs and cutting back flights to save money, a plane that holds 800 people isn't that good an idea. Couple that with the fuel issues and it becomes less desirable. Oppositely, Boeing currently has 500+ orders for it's small, fuel efficient 787 Dreamliner.
5) Airbus has lost some major contracts for the A380 and it's future existence is in question. Both UPS and FEDEX canceled pre-orders for the A380 citing cost overruns, delivery delays and all of the issues I have listed above. Both then took out contracts with Boeing for 777 aircraft which will fit into their existing fleet without any changes required.
6) At least one non-US airline has canceled their order for the above mentioned reasons (Emirates IIRC)
7) Both Singapore Air and Virgin Atlantic have placed orders but neither has announced expected in-service dates as the deliver of the aircrafts continues to slip, initial delivery is now slated for 2013. The real possibility exists that one of them may cancel their orders.
In summary, cool airplane, wrong time to build it though.