We have a piping library that is added to our AutoCAD LT 2013 using the menuload command, then adding the file to the support path in Tools>Options.
On one of our Win7 64-bit machines, when the user restarts Autocad, the piping library is missing as if it was never added before. I installed SP 1.1 and that did not solve the issue. I have other Win7 and Win8 64-bit machines using the piping library and those are not having any problems.
I have not yet tried uninstalling and reinstalling AutoCAD, I was hoping to find a solution before I go ahead and do that.