...I found the latest driver software for the 3800 on the Epson (USA) site, dated 5/3/13 and installed it. After re-booting, I tried again to print with the 3800, only to get the same error message: "You need to install software to use this printer.
There is no such driver "dated 5/3/13" for the Epson Stylus Pro 3800. The latest driver released in the USA was version 8.64 on 10/10/2011. It is compatible with OS X 10.8.x, 10.7.x, 10.6.x, and 10.5.8. You did not state which OS you upgraded from and what version of the print driver you had before the OS upgrade. That said, did you repair disk permissions after upgrading to 10.6.8?
I depend on the 3800 for professional work, and certainly can't afford to replace it...
but you stated
A few months ago I upgraded my system to OS X 10.6.8. Yesterday, I tried to use my Epson Stylus Pro 3800 inkjet printer fro the first time since the upgrade,
which implies that you use the Epson 3800 occasionally, so "depend" seems...
Thank you for your response.
1. I have downloaded and installed printer driver version 8.64 from the site suggested;
2. I have repaired disk permissions again;
3. I am still getting the same error message as above: "You need to install software to use this printer....";
4. My previous operating system was OS X 10.5;
5. Other Epson printers work correctly; it is only the 3800 which refuses to perform.
Any further suggestions gratefully received.
Further to this problem:
I removed all the existing Epson printer files from my computer.
I also downloaded from the same Epson site Common Updater v.7.0. Once this was installed, a new and different error appeared:
Error: /Library/Printers/EPSON/InkjetPrinter/Filter/rastertoescp.app/Contents/MacOS/ra stertoescp failed
A Problem Report also appears when attempting to print:
rastertoescp quit unexpectedly
The opening lines of the detailed problem report are as follows:
Process: rastertoescp  Path: /Library/Printers/EPSON/InkjetPrinter/Filter/rastertoescp.app/Contents/MacOS/ras tertoescp Identifier: rastertoescp Version: ??? (???) Code Type: X86 (Native)
Parent Process: cupsd 
Date/Time: 2013-05-16 09:43:12.737 +0300 OS Version: Mac OS X 10.6.8 (10K549)
Report Version: 6
Anonymous UUID: D9027E0F-CD1F-4E69-9DCC-3EED71B6FAF0
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x000000005d8918ec
Crashed Thread: 0 Dispatch queue: com.apple.main-thread
Thread 0 Crashed: Dispatch queue: com.apple.main-thread
0 ??? 0x5d8918ec 0 + 1569265900 1 ...pson.ijprinter.rastertoescp 0x0000297a main + 230 2 ...pson.ijprinter.rastertoescp 0x00002522 start + 54