but then I simply cleaned it a bit and the it worked. Now I doesn't.
By cleaned a bit did you clean the DVD drive laser lens?
If you open the drive a qtip with rubbing alcohol(Isopropyl 70-90% higher better) can be used to clean the lens.
Be very gentile.
In most cases it is just dust and even a lens cleaner(cd with little fine hair bristles on it) will work.