This error will occur when there is a corrupted configuration file. To fix the error you will need to delete the rezstream.ini file from the rezstream folder.
Follow these steps to find and delete the file. (exit out of rezstream if it is open)
1. Open your C: drive in windows explorer.
2. Find the rezstream folder (either in Program Files or Program Files(x86))
3.Open the rezstream folder and find the rezstream.ini file. Your computer may not be showing you the file extensions so look for a file named rezstream that is a configuration settings file type.
4. Delete this file and restart RezStream.
5.Once you restart RezStream you may need to re-select your printers.
This video also shows how to find the file: http://screencast.com/t/ZBWKpe84A