Minecraft Launcher doesn´t want to start

Hey, Yesterday I bought Minecraft Premium on minecraft.net and i installed minecraft launcher. And now I don´t can start the Minecraft Launcher, I tried it very often. please help me, because I payed and now I don´t can start it! ;( in may i played demo, but now I dont can start the launcher. nothing happen if I start the launcher. Sorry my english is bad. please help me! (i can speak german)