I've been using a Canon N1240U USB scanner with Win2K for a long time and things were fine until today. I went to scan something and my software said there was no TWAIN. I've reinstalled the software three times and I'm getting the same result... but actually, it's something bigger than that:

The Unplug/Eject Device thing in the Tray doesn't show the scanner. When I plug the scanner into the USB, the computer acknowledges it is there and loads the drivers, the Device Manager shows the scanner and says it's working fine, but the USB thingie claims it doesn't exist and the Cam/Scan control panel item says the device is there but "unavailable". Other USB devices such as my CF reader are present and functional, and changing USB jacks didn't change anything.

The only thing done differently TWAIN-wise is that I had attached a camera, but I have uninstalled the software that came with that and the two had been working together previously.

Any idea what's causing the scanner to be acknowledged as being on the USB by the computer but then not be listed as a useable device?

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try to uninstall the universal serial bus controller within device manager and restart the computer. Upon restart it will start the found new hardware prompts and reinstall the usb controller. Now plug in the scanner and see if it's a go.

Nope.

I removed all USB listings in Device Manager, rebooted, it added all the hubs and roots, then plugged my USB devices back in including the scanner and Windows latched onto them, but the scanner still isn't listed in the USB devices.

Next idea?

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Try it on different PC. I suspect a failing scanner.

Cameras and scanners both use ASPI drivers. One of your devices may have changed the ASPI layer drivers. If you uninstalled a camera you may have removed a dll that was needed for the scanner also. For some info on this issue read this article. http://aspi.radified.com/
I don't have a good handle on this issue myself but I do know this could be your problem.
I did notice that I have a subfolder under the Twain_32 folder in my WinNT directory for both my USB camera and my USB scanner.

OtheHill: No such luck. I reinstalled the camera and made sure that it was recognised correctly (both displaying stills taken detached from the computer and video taken attached to the computer). Plugged in the scanner, usual gyrations. Then I checked the USB thing and, once again, the scanner wasn't listed or accessable.

ClydeB: Here's where it gets goofy, because you may be something close to right (to my surprise). The motherboard has four 1.1 jacks, and I added a 2.0 card with four jacks a couple years ago (due the the fact that my 1.1 runs slower than standard, thus data from the scanner bottlenecked on full-platen images or high-density scans -- I bought that 2.0 card specifically for the scanner!). My 1.1 camera's video would cause the machine to dump the camera after 20 seconds due to such bottlenecking, but stays up endlessly in the 2.0). Between paragraphs of this email I plugged the scanner into a 1.1 jack for grins and now the scanner IS LISTED in the USB items. When the driver setup was finished it wanted me to reboot, and I decided to finish this post first. :) I'll let you know if this was the fix-all, and wonder if this will now let me use it in the 2.0 again because I'm gonna be very sad if it can't work there no mo'.

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No. The scanner showed up in the USB list after I plugged it into the 1.1, but once the machine was rebooted as it asked, pttthhtt, not listed. Device Manager still says it's there and functional, Scan/Cam control panel says it's there but unavailable. Will have to try the scanner on another machine -- and neither of the other computers I have bear USB ports -- or something. :(

Any other bright ideas out there, in case it is the USB doodads of Windows 2000?

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Okay, this takes the cake...

Following previous advice, I installed the scanner on my wife's computer -- and this required installing the USB 2.0 card I've been using on my own machine. The bottom line is that the scanner scanned on her machine, showing the scanner and the USB 2.0 card work fine.

So it's a Windows 2000 issue.

But I have thought of a solution for that, necessitated by how my computer behaved when I put the card back in and turned it on -- RAS is missing now. Windows lost my connectoid and won't let me create a new one. And it still doesn't show the scanner in the USB list except when it's disabled.

Thanks for your suggestions; too bad none of them addressed the root cause which is still unknown (hey, I thought deleting the hubs & hosts would fix stuff too!).

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The

Did you take a look at the article about the ASPI drivers?

OtheHill: Yes, I did, thanks. And as previously stated (or was trying to, I seem to have not finished the sentence I started), since I suddenly lost RAS I had no choice but to nuke and pave Windows. I'm back up and my scanner works again.

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All's well that ends well. You may want to download those ASPI utilities now and run the aspichk. That way you will know what version of those files works. If it gets coppurted again you may be able to repair without a reinstall.

OtheHill: Yeah, one way or another -- and it probably took less time to nuke and pave than to fix the problem directly. For the record, I'd updated my ASPI layer a few weeks ago (for the benefit of my CD burner software) and ASPICHK said I had the latest versions. This isn't to say something didn't get corrupted recently, but judging by how the OS melted down it was just the first sign of worse things.

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The latest version isn't always the best. Many folks have had trouble with the latest and have rolled back to 4.60.