Game-based learning (GBL) environments are shown to support open-ended inquiry, collaborative learning, shared knowledge creation and decision-making processes. The study at hand focuses on examining students' descriptions of problematic situations and collaborative learning in a virtual simulation game. We were interested in what kinds of challenges the students encounter in virtual teamwork in GBL. Data of the study stems from gaming sessions in which teams of 5-7 students worked in a virtual learning environment and steered their simulation companies' supply chain in real-time. Students' reflection assignments were analyzed with qualitative content analysis. Our results show that during the sessions students encountered communication challenges, collaboration challenges, organizing challenges and skills and competence issues. As all these are typical for modern dispersed collaborative work, we can state that the game-based course of this study provided the students with opportunities to rehearse and solve these challenges in a virtual working context. Our results emphasize the importance of providing students an opportunity to exercise collaboration and problem-solving skills in authentic, safe and inspiring settings, and that simulation games represent a feasible context for this.