I have a mintyboost, a solar panel 6V and a USB / DC / Solar Lithium Ion/Polymer charger - v1.0. I connect the boards as in the following picture:
Do you have a LiPo cell connected also?
Is the cell charged?
Is the solar panel in full sunlight?
For example, if I connect 7V to mintyboost, the output voltage is not 5v, the output voltage is about 7V.
As the name implies, the MintyBoost is a Boost converter. It is not designed to regulate input voltages higher than the output voltage and you can damage it with too high an input voltage. The maximum safe input for the MintyBoost is 5v.
When connected as shown on the product description page, the maximum input voltage to the MintyBoost will be 4.2v - the output voltage of a fully charged LiPo cell.