This behavior is caused by an incompatibility between OT/PPP 1.0, and the Global Village PowerPort Platinum Pro PC Card. This is the PC card that has combined Ethernet and a 28.8 kbps modem.
Global Village has released updated software that should resolve the issue. It is available from the Global Village software update site:
ftp://ftp.globalvillage.com/pub/software/mac/PP_PC_Card_beta_OT_PPP.sea.hqx
Note: The problem described can also occur with Apple Remote Access 3.0.