Prices not setting

I just downloaded and installed the Lite version of marketpress(version 2.9.5.6) and the only issue I have at the moment is the fact that I can’t get the prices to set at all. What I have noticed happens when I try to set the price is that once I enter the price I want and click update the screen goes completely white and I have to use the back arrow to get back to the product page. I have also noticed when it does and I open the shop page on another tab, there is no price set. I am using the MYCRED system(version 1.6.9) instead of normal currency. I am really hoping there is a way to fix this without having to upgrade.