I've checked the syslog and when I start the pptp service, I get practically the same error that cuma gets with pptpd:
May 24 15:46:19 fritz daemon.notice pppd[2148]: pppd 2.4.4 started by root, uid 0
May 24 15:46:19 fritz daemon.info pppd[2148]: Using interface ppp0
May 24 15:46:19 fritz...