I am new to Edwin and MIT-Scheme, but my recent installation under MAC OS X Yosemite works fine, so I think I know how Edwin should work.  My installation of Edwin and Scheme on Win 7 has no problem if I simply work within the Scheme buffer that first comes up when I call Scheme with the --edit option (via a Windows shortcut).  That is, using C-X C-E, I get appropriate responses when I evaluate legal expressions, and I get appropriate error messages if I attempt to evaluate an illegal expression.  However, once I open a separate file buffer for a .scm file and work from that buffer, I get different behavior.  There is no problem as long as I evaluate just legal expressions (using C-X C-E):  I get the appropriate response in the mini-buffer.  However, when I attempt to evaluate an illegal expression (such as (+2 2) or (cub)), I get no response in the mini-buffer or in the main buffer.  Further, when I proceed to attempt to evaluate anything after that (legal or not), I get the message "REPL needs response before evaluation will be enabled" in the mini-buffer. I have found no way to proceed after that except to close Edwin.  I do not know if this is actaully a bug or if it is some sort of installation error, possibly involving an environment variable.  However, I accepted all the defaults when I installed and did not tamper with any enviroment variables.  Also, I experience the same problems whether I install as an administrator or as an ordinary user.  Finally, I have tried both versions 9.0 and 9.2 of MIT-Scheme, and get the same behavior.