may help.
What Mac and what version of OS X are you running?

Does that Iomega drive have it's own power supply or is it drawing power down the USB cord?
If it is, then there is a possibility that the iPod and the Iomega combined, are drawing too much power.

Get a power adapter for the Iomega
Get a USB hub and plug the devices into it.

If you have an iMac. Shut it down, disconnect ALL peripherals except the keyboard and mouse.
Remove the power cord.
Wait 5 minutes
Plug it back in and boot it up.

Leave the Iomega disconnected for now. Connect the iPod and see if your iPod reappears in iTunes.