I am having the exact same problem as JulesMazur - same Epson scanner (4990), same problem recognizing separate slides, etc. Big project stopped in my tracks. I tried your solution, Matt, and it doesn't seem to work. I downloaded the 10.6 drivers and got something called the Epson ICA Installer. Opened it up, it seemed to process (bars running showing me progress) then nothing. Can't find the application, if that's what it is, anywhere - just the ICA installer and we go through the process all over again. I can no longer even FIND my scanner unless I go to System Preferences- Printers & Scanners - and click on my device. I'm sure I get the same thing Jules does - a very rudimentary screen allowing me to pick very few options (photo/film negatives/color positives). Gone are the different formats this scanner offered: Home Mode, Full Auto, etc. And when you try to scan slides, it scans the whole flatbed, slide holder and all.
I did have one other thought (and I've never tried anything close to this, being a real neophyte, computer-wise). Since I still have the actual disks of Snow Leopard when I upgraded to that (and the scanner worked fine with that), is it possible to partition the hard drive, and install Snow Leopard as the operating system for the other drive, and then re-install the software for the scanner on that hard drive and do all the scanning there? In other words, is it possible to run two different OSs on the same computer by partitioning the hard drive?
The other thing I wondered is whether our inability to work this has anything to do with Silverlight. I'm trying to remember why I have that on my system, but I'm thinking it came with the scanner and the scanner software. Would upgrading the version of Silverlight (if there IS an upgrade) put us back in business?
Thanks!