OK, what you could try is deleting the variables and then re-creating them again with the existing name (LIB) or create a new variable name on the PC and change the script so it looks for the new variable, is there any way that you can use the force command in the JS script to tell the PC to connect to the desired printer???
1 more thing is to try and install con2print. its exactly what you need to do and its what i use at all of the schools that i look after.
here is the download link........ its all basic scripting, you just unzip and paste the con2print.exe into your Netlogon folder and create a new .bat file calling con2print. any probs message me.
http://thisishelpful.com/Downloads/p13_sectionid/1/p13_fileid/1
Hope this might help.