Software misconfigurations are time-consuming and enormously frustrating to troubleshoot. In this paper, we show that dynamic information flow analysis helps solve these problems by pinpointing the root cause of configuration errors. We have built a tool called ConfAid that instruments application binaries to monitor the causal dependencies introduced through control and data flow as the program executes --- ConfAid uses these dependencies to link the erroneous behavior to specific tokens in configuration files. Our results using ConfAid to solve misconfigurations in OpenSSH, Apache, and Postfix show that ConfAid identifies the source of the misconfiguration as the first or second most likely root cause for 18 out of 18 real-world configuration errors and for 55 out of 60 randomly generated errors. ConfAid runs in only a few minutes, making it an attractive alternative to manual debugging.