I've done some searching on this and people blame cables, media transport, etc...
-My S4 can connect to my work Win7 PC reliably so far (HP Desktop)
-My S4 can NOT connect to our home Win7 PC (Toshiba Laptop). Nothing shows in DeviceManager or FileManager. Rebboted PC and S4.
-Wife's S4 connected to our home Win7 PC one time, copied some files to it.
-Wife's S4 can NOT connect to our home Win7 PC any more (with same cable but since have tried two cables one being the original Samsung)
Has anyone found a reliable fix for this? My phone's flash is filling up with pictures/videos.