Nikon ls-5000 ED stopped accepting negative strips. Was working.

SOURCE: Drivers for Nikon LS 5000-ED

Try these links:

http://www.silverfast.com/product/fr.html?product=436
http://www.xpvistasite.com/super_coolscan_5000_ed_13548.htm

'hope that helped.

SOURCE: Nikon Coolscan 5000 ED not scanning

Have you tried resetting the scanner itself?

SOURCE: vertical banding

Well not a complete solution but. . . It will help. 1st Digital Ice will screw up when trying to use it's infrared on Kodakrome so either don't use it or better yet don't use Nikons scanner utils. I use both Silverfast and Vuescan and will never look back yes they both solved this but the real issue is inside but do download a trial of vuescan before you go any further.
Your problem might be a cleaning of the mirror since mounted slides might "curve" in the frame differently and accentuate this issue. Look at this site I clean mine once every 6000 scans which works out to about once or twice a month.

I also recommend (a must do) is run your scanner on its side if you own a sf-210 feeder you already are so look at how this unit attaches on nikon's site or in your manual and do it. This way the guts are on their side (mirror not lying almost flat for all the dust to fall onto it).
Good Luck Morphoto.ca

SOURCE: Nikon cool scan 8000 How to load 2 1/4 by 2 1/4 negs on this tray

There is a lock on the oper side. release the lock and the other side also opens like a door

SOURCE: SA-21will not pull film strip into chamber

Put the film in after it is powered up. The unit needs to run through a power-up and calibrate cycle first. Once powered up, the until will feed the film in once it reaches a certain point into the machine.

The unit is supposed to kick the film back out when you close down the scanning software. If your film ever gets stuck try this to get it out. DO NOT force the SA-21 out of the machine with film stuck in it.