The reformers took issue with the sale of indulgences. According to wikipedia indulgences are the full or partial remission of temporal punishment due for sins which have already been forgiven. The indulgence is granted by the church after the sinner has confessed and received absolution. The belief is that indulgences draw on the storehouse of merit acquired by Jesus' sacrifice and the virtues and penances of the saints. They are granted for specific good works and prayers.
The abuses with indulgences occurred when the church used this belief to raise money for various causes. The reformers saw the church selling forgiveness for cash.
As far as I know most abuses of selling indulgences ended in the later 1500's. There is still some noteworthy debate over the issue, but I don't think it's the kind of debate that should cause one member to reject the faith of a brother or sister in Christ.
Understanding Indulgences: http://www.wsu.edu/~dee/GLOSSARY/INDULGE.HTM
A Catholic Position on Indulgences: http://www.catholic.com/library/Myths_About_Indulgences.asp
Disclaimer: About This Blog
THIS BLOG IS: my personal journey of how I am rethinking some of my spiritual beliefs.
THIS BLOG IS NOT: intended to point fingers at people who I think are wrong.
I do not believe the final judgement will be based on how many correct answers we get on a theology exam. I believe many people throughout history have had genuine relationships with our Lord and Saviour Jesus, despite holding questionable beliefs and practices. I make no claim to having it all figured out or being your judge. If we end up disagreeing over these topics I pray we can find a way to demonstrate grace.