Sounds like you scorched your chocolate. Did it smell kinda burnt? If you scorch chocolate...throw it out...can't use it for anything, except revenge maybe...hmm??? lol
Rules of melting chocolate...
1. Heat VERY SLOWLY
2. Keep Stirring...let it heat up equally. Some compounds of the chocolate melt at lower temperatures than others...(cocoa butter melts at 98 degrees farenheiht....that's why it melts in your hand...) Also, a higher ratio of cocoa butter will give you chocolate that melts very smoothly. Most supermarket chocolate (read chips, bars, even some of the baking stuff) has an emulsifier called lecthin in it which will make it harder for the chocolate to melt.
3. Keep ALL moisture, especially water, in a galaxy far, far away
4. NEVER...EVER...EVER...EVER...you get the point...let chocoate get above 120 degrees Farenheit...otherwise it will scorch and ruin it.
If you are using chocolate chips, they will hold their shape until you start stirring them.
Now tempering chocolate...whole different ball game.
Happy Chocolating! :)