Nowadays many schools in higher education implement problem-based learning to foster active learning processes by students. In some schools with a number of years of experience with this approach, phenomena can be observed which indicate signs of wear. The implementation of a large-scale innovation such as problem-based learning (PBL) seems to provoke different activities and attitudes in those actors who are most involved. Students and staff members seem to behave in a way which could be counterproductive to the development of self-directed learning. In the first part of this paper, we briefly describe the cognitive psychological background of PBL. In the second part various adjustments observed in problem-based curricula and their effects on students' learning are analyzed. Arguments are presented about adverse effects on the implementation of this educational innovation. Special attention is given to teachers' concerns. In the third part suggestions are made about ways to revitalize PBL processes as well as suggestions about effecting educational innovations on a more solid basis.