The 6ui.dll error message stems from the HP LaserJet 4100 Series Printers. If you have a HP LaserJet 4100 Series Printers, then a file was corrupted in the installation process, and it needs to be reinstalled.
If you have been using the printer for a while then it is a registry error. This is common enough as registry errors happen with day to day usage. Therefore, it is recommended by computer experts to run a registry cleaner on a regular basis.
Below is a button to run free registry scan. It will show you all the registry related errors on your computer. Once ZookaWare PC Cleaner has identified all the problems, you can invest in ZookaWare PC Cleaner and clear them up. Then set ZookaWare PC Cleaner to run on a regular basis, so you won’t ever encounter a registry error again.