My sister is getting the same problems, Minecraft opens as vanilla.
mac OS 10.7.5, Intel core 2 Duo 2.4 GHZ, 4GB ram. hers seems to run differently to mine, where she doesn't need to use the export command. This might be linked to that.
If you have Mac-Make sure you have Java 6
If you have 64 bit windows: Get Java 7 u9 x64
If you have 32 bit Windows: Get Java 7 u9 x32
If you have 32 bit Java you can't allocate more than 1gb of RAM to the launcher.
Make sure your antivirus' and firewalls are set to "allow".
If you internet connection is slow: do this