you should be able to, but heres the ps3 folder structure/layout below:
MUSIC
Album Name (when copying whole album to drive)
Song title 01.mp3
Song title 02.mp3
Song from another album.mp3 (when copy individual songs)
PICTURE
CIMG1387.JPG
PS3
EXPORT
BACKUP (created via PS3 backup feature)
200911131808 (date backup was performed, format=YYYYMMDDHHMM)
archive.dat
archive_00.dat
archive_[XX].dat
archive2.dat
archive2_00.dat
archive2_[XX].dat
PSV (PS1/PS2 game saves)
BESLES-544543032.PSV
SAVEDATA (PS3 game saves)
BCES00001_PROFILE
ICON0.PNG
PARAM.PFD
PARAM.SFO
PROFILE.SAV
BCES00078-GAMEAUTOSAVE
ICON0.PNG
ICON1.PAM
PARAM.PFD
PARAM.SFO
PIC1.PNG
SND0.AT3
USERDATA.DAT
THEME (new in firmware 2.0)
themename.p3t
UPDATE (firmware update file)
PS3UPDAT.PUP
VIDEO
Name_of_video.mp4
I know the ps3 can be fussy with the locations of media files and updates, have you tried backing up your ps3 the process can create folders and verify compatibility, although at the very least it should still show up as a usb connected device in the video, music and pictures section, have you tried the other usb ports on the ps3, also sometimes the ports on certain usb devices can't supply enough power so you need a twin usb cable:
http://www.ebay.co.uk/itm/Twin-USB-2-0-Tape-A-to-Mini-5Pin-Data-Power-Splitter-PSP-Enclosure-Cable-Wire-PC-/270856163980?pt=UK_Computing_USB_Cables&hash=item3f1049128c
Also if you have a usb hub try using it to see if it makes a difference.