My name is XXXXX XXXXX I'd like to help you with your Zip Disk problem. I would agree with the user forum that it sounds like the Zip Disk is in an older format that Mac OS 10.6 can read but cannot write to. This is also a result of their not being any drivers for 10.6 yet.
Unfortunately, there's not much that can be done until Iomega comes out with drivers for 10.6. I do have another suggestion for you, however. Zip Disks are a very old technology and don't hold very much, a Zip 100 disk can only hold 100 Megabytes of information.
I would suggest going out and getting a USB Thumb Drive. You can get a 2 Gigabyte one for roughly $30. A 2 Gigabyte thumb drive can hold the equivalent of nearly 20 Zip 100 Disks, and can fit in your pocket. You also don't need a special drive to read it, you simply insert it into any computer and have access to your information.
I would suggest picking one of these up, you can get them anywhere, BestBuy, Staples, Target, Walmart, and then copying all of your information from the Zip Disks to the Thumb Drive.
Please let me know if you have any further questions and don't forget to click the green "Accept Answer" button so that I can get paid for my service. Thanks.