A primary goal of working memory research has been to understand the mechanisms that permit working memory systems to effectively maintain the identity and order of the elements held in memory for sufficient time as to allow for their selection and transfer to subsequent processing stages. Based on the performance of two individuals with acquired dysgraphia affecting orthographic working memory (WM; the graphemic buffer), we present evidence of two distinct and dissociable functions of orthographic WM. One function is responsible for maintaining the temporal stability of letters held in orthographic WM, while the other is responsible for maintaining their representational distinctiveness. The failure to maintain temporal stability and representational distinctiveness gives rise, respectively, to decay and interference effects that manifest themselves in distinctive error patterns, including distinct serial position effects. The findings we report have implications beyond our understanding of orthographic WM, as the need to maintain temporal stability and representational distinctiveness in WM is common across cognitive domains.