Nope, didn’t even see the folder which had previously seen on the laptop. I restarted everything as well to do as much resetting as I could.
Have you confirmed that the files are compatible with the PMC? Perhaps if there isn’t a single compatible file in the folder PMC chooses to not display it at all. I don’t use PMC so I can’t say precisely, but on my 360 it completely ignores anything that’s not in a format it can use and it doesn’t preserve original folder structures instead pooling media into a single interface when using WMC. Not sure what it does with USB storage though.
Since you’re using TVersity I’d keep investigating the file-type issue. TVersity’s entire purpose for being is to transcode media so perhaps you don’t have any formats that are native to PS3.
When the folder was in “My Videos” on c: PMS saw the folder (and files). I moved it whole and intact to f: (the external), and it can’t see it/them. Weird.