This may not be the only problem with the Iomega 6.0 driver on G3 Macs. In particular:
Freeze when mounting external drives Carl Braga writes: "Just received one of the 'Rev 2' PowerMac G3 266 Minitowers. They have the CD-ROM, ZIP and Internal Hard Disk all on the ATA bus. With the release, comes a new Iomega extension version 6.0 which handles the new ATA based ZIP (no longer SCSI). When this is loaded, either one of my two Fireball SCSI externals formatted with HDT 2.5.2 drivers, will freeze the system when they are mounted. Disabling the Iomega 6.0 extension fixes this."
Andy Sheimo had what may be a related problem. He states: "I cannot put a Zip drive on the secondary channel of my G3 Mac with the Rev 2 logic board. It will show up with things like Drive Setup and SCSI Probe but it will not mount."
Freeze when waking up from sleep Matt Vlasach confirms a similar problem: "I have a new G3 Minitower. When I wake it up from sleep, the mouse can move but you can't click. The green power light on the tower remains off when it is supposed to turn back on. The cause is a conflict between Energy Saver and Iomega Driver 6.0! It will hang the machine when enabled in the Extensions manager and you try to wake up the machine."
Sometimes changing the load order of the Iomega driver fixes these sort of problems. I am still investigating this.