The instruction at "0x77c71861" referenced memory at "0x0000004e". The memory could not be read.

Windows Server 2003 SP1 Terminal Services using remote desktop (no Citrix).  Remote desktop is configured to connect automatically to local printers when logged onto the remote computer.  When users report either a blank blue screen when they log into this server (not a blue screen of death) this error message is displayed on the server when I check the server.  The server itself has not crashed.  Other users report printers are not being connected when they log in.  I've run hardware diagnostics to check memory - no problems reported.  Dr. Watson logs don't have anything either.  After I respond the the dialog window for this error, the user can log in.  The only thing that changed on the server was adding a printer driver for an HP printer.  THis started about the middle of May.  Has anyone had similar problems or know of a fix?