Under OS/2 WARP, if a folder is set to NOTVISIBLE=YES and is then set to be NOTVISIBLE=NO, the system will hang.
This is a bug in the current release of WARP. The supposed workaround: Force the invisible folder to open with OPEN=DEFAULT before changing the setup string NOTVISIBLE (see APAR PJ16250 fixed in WARP 3 FixPack #12).