As per the "LaTeX Support for NetBeans" page at http://latex.netbeans.org I have manually installed the module from
http://latex.netbeans.org/files/documents/162/785/org-netbeans-modules-latex-auc.nbm. The "Update Center for LaTeX
Integration for NetBeans" now appears in the "Update Center Wizard" dialog. After selecting "Next" the dialog
"Connecting to the Update Center for LaTeX Integration for NetBeans..." takes a very long time to process any ultimately
"Unable to connect to the Update Center. Check your proxy proxy settings or try again later. The server may be
unavailable to this time."
I am able to connect to the other update centers without any problems. It seems this Update Center module has a bug or
the server it points to is unavailable.
I guess the server was unavailable at that time or it has already been resolved because I don't have any problem
connecting to the update center for latex.
Sorry I missed you were using NetBeans 5.5.1. I only know it works in 6.5.