Why doesn’t windows explorer show my removable / USB drive even though the command prompt does?

I'm running WinXP SP2. Around 50% of the time, when I slot in my USB drive. Windows explorer refuses to show the drive.

1. If I click on the Safely remove hardware icon on the tray,
   I can see a menu item for the drive - say drive G: (the light on the USB drive is also on)
   
   
   
   
   • If I type in G: into the address bar of explorer,
     it says 'Cannot find...'
   
   
   • If I type in G: into a command prompt window,
     it works and I can do a dir to see the list of directories on the drive.
   
   

To fix this, I've to remove-reinsert the pen-drive. But doing it every day is annoying. Also this happens only on this machine.. I use this drive on my home machine and it works flawlessly each time.

Can anyone suggest things that I could try ?

Thanks for reading...