When you have a mounted cifs share, and the server for any reason goes offline, the machine is not allowed to enter the suspend mode. Of course, this is a error condition, but I don't see why this should prevent entering suspend mode. As a fair-use example: I have two computers at home, both have reciprocal cifs mounts from each other. I cannot suspend both of them because of this bug.
*** This bug has been marked as a duplicate of bug 11050 ***