PPP error in Windows 2000

The VPN is similar to what I am try to set up here in my office. We’re using the IBM glpbal dialer however as to connect to a server on IBM farm and from there to our Exchange servers. However on a W2K laptop(IBM T20) no connection can be made and the error is that the two machines cannot settle upon a PPP setting. I’ve called the dialer vendor and they have suggested removing DUN and reinstalling it to 2K. I have other 2k laptops that connect fine only these T20 have the issue.