DX6480 and DX3600 have stop't working in win xp help needed

I have both cameras hooked upto windows XP media center through there own 
docks and all has been fine until monday just gone.

I took some pictures with my DX3600 and connected to the pc as usual, 
pressed the transfer button, windows made the usual sound to acknowledge 
that my camera was connected but it did not show in My Computer.

I then tried my DX6480 and the same thing, Win makes the noise that I'm 
connected, but no show in My Computer.

if I go to Hardware Device Manager, both cameras show up, but I can't
access 
them.

can anyone help?

regards
           Margaret