Hi all!
I'm glad to say that macOS 10.4.4 seem to (partially) fix the problems, at least for my Samsung CLX-3815FW.
I say partially because now I can scan in color and save to almost all formats. The only format still with problems is PDF.
Savings as JPEG, JPEG200, GIF, TIFF, BMP and PNG works now.
When saving as PDF, if not "combining" (putting all scanned pages in the same PDF file), the produced PDF is not readable. If "combining", Image Capture just crashes!!!
I've checked the produced PDF file (created in non-combining mode) and it looks like some, even all, of the scan image's data is there, it's just the headers that are wrong or corrupted (the "file" command that examines the start of files to determine it's type can't recognize it).
So we are getting there. Too bad that PDF and "single-PDF" (combine) that are the most useful options are still not working. But at least Apple recognizes that the problem in on their turf, not the printers' manufacturers.
I have stong hopes for 10.4.5 (but with the Mail issue with GMail, my guess 10.4.5 is just around the corner, so 10.4.6 is more likely).
I would love to see other reports regarding other printers.