From the Build Window, right click and select "Send Compile Output to Edit Window", then go to the top Menu > Documents > Select Mode... The current mode should show up as Process. There should be a menu item named something like "Process Options..." If not, then you have changed the document mode of the Process buffer and this explains the odd behavior. From the SlickEdit command line, type the command "select-mode Process" to correct it.
If not, can you reproduce this issue from a default configuration ?