Have you tried the new drivers. if you are using Windows xp, these drivers look fairly new. I have a precision scan 2110 with the 4.0 drivers and it works great in elements 2.0. I am guessing about your operating system because it never was specified.
From the hp site:
Microsoft Windows XP
description date rev size
CD - HP ScanJet Scanner 4570c/5500c Scanning Software, v1.2 for Windows, and v5.5.6 for Macintosh 2003-03-31 Win: 1.2;Mac: 5.5.6 N/A
CD - HP ScanJet Scanner 4570c/5500c Scanning Software, v1.2 for Windows, and v5.5.6 for Macintosh, with ArcSoft Photo Funhouse 2003-03-31 Win: 1.2;Mac: 5.5.6 N/A
CD-HP ScanJet 2300/3500/4500/5500 Series Photo and Imaging Software, v2.0 2003-04-17 2.0 N/A
HP Photo and Imaging AOL version 8.0 update 2003-04-15 1.0 185.00 KB
hp photo and imaging software 2003-06-11 2.0 205.10 MB
HP ScanJet 4500/5550c, 4570/5500c series software v1.2 sleep mode/ PC reboot update for Windows XP and Windows 2000 2002-10-02 1.2 595.50 KB
HP Photo and Imaging Software Update, v1.2 for problems saving PDF and Text files on non-English language systems 2002-10-17 1.2 5.65 MB
If what you were looking for is not listed, then it is not available for downloading from the web in this language.
Just a thought.
Gregory, did you Repair Permissions before and after your installations? Too late to do a "before" now :) but if you didn't do the "after", run it and see if it helps. It often smoothes out rough edges like you're describing.