[pptp-server] what am I doing wrong here?

[Heusden, Folkert van]

I get this error:

Mar 19 13:46:41 linux pptpd[2688]: MGR: Launching /usr/local/sbin/pptpctrl
to handle client
Mar 19 13:46:41 linux pptpd[2688]: CTRL: local address = 192.168.0.235
Mar 19 13:46:41 linux pptpd[2688]: CTRL: remote address = 192.168.0.230
Mar 19 13:46:41 linux pptpd[2688]: CTRL: pppd speed = 115200
Mar 19 13:46:41 linux pptpd[2688]: CTRL: Client 192.168.0.14 control
connection started
Mar 19 13:46:41 linux pptpd[2688]: CTRL: Received PPTP Control Message
(type: 1)
Mar 19 13:46:41 linux pptpd[2688]: CTRL: Made a START CTRL CONN RPLY packet
Mar 19 13:46:41 linux pptpd[2688]: CTRL: I wrote 156 bytes to the client.
Mar 19 13:46:41 linux pptpd[2688]: CTRL: Sent packet to client
Mar 19 13:46:41 linux pptpd[2688]: CTRL: Received PPTP Control Message
(type: 7)
Mar 19 13:46:41 linux pptpd[2688]: CTRL: Set parameters to 1525 maxbps, 64
window size
Mar 19 13:46:41 linux pptpd[2688]: CTRL: Made a OUT CALL RPLY packet
Mar 19 13:46:41 linux pptpd[2688]: CTRL: Starting call (launching pppd,
opening GRE)
Mar 19 13:46:41 linux pptpd[2688]: CTRL: pty_fd = 4
Mar 19 13:46:41 linux pptpd[2688]: CTRL: tty_fd = 5
Mar 19 13:46:41 linux pptpd[2688]: CTRL: I wrote 32 bytes to the client.
Mar 19 13:46:41 linux pptpd[2688]: CTRL: Sent packet to client
Mar 19 13:46:41 linux pptpd[2654]: MGR: Reaped child 2688
Mar 19 13:46:41 linux pptpd[2691]: CTRL (PPPD Launcher): Connection speed =
115200
Mar 19 13:46:41 linux pptpd[2691]: CTRL (PPPD Launcher): local address =
192.168.0.235
Mar 19 13:46:41 linux pptpd[2691]: CTRL (PPPD Launcher): remote address =
192.168.0.230
Mar 19 13:46:41 linux pptpd[2688]: GRE: read(fd=4,buffer=804d780,len=8196)
from PTY failed: status = -1 error = Input/output
error
Mar 19 13:46:41 linux pptpd[2688]: CTRL: PTY read or GRE write failed
(pty,gre)=(4,5)
Mar 19 13:46:41 linux pptpd[2688]: CTRL: Client 192.168.0.14 control
connection finished
Mar 19 13:46:41 linux pptpd[2688]: CTRL: Exiting now
Mar 19 13:46:41 linux pppd[2691]: The remote system is required to
authenticate itself but I
Mar 19 13:46:41 linux pppd[2691]: couldn't find any secret (password) which
would let it use an IP 
address.

what can be a possible cause of this?