I also did the same thing. I installed BandwidthD around 9:30am (judging from BandwidthD's daily graph) yesterday, and around the same time RRD stopped updating any of its graphs.
After reading your post, I checked the system logs for "lighttpd" entries, and saw the following:
Dec 1 09:23:32 lighttpd[30518]: (mod_fastcgi.c.2543) unexpected end-of-file (perhaps the fastcgi process died): pid: 31140 socket: unix:/tmp/php-fastcgi.socket-1 Dec 1 09:23:32 lighttpd[30518]: (mod_fastcgi.c.3282) child exited, pid: 31140 status: 0 Dec 1 09:23:33 lighttpd[30518]: (mod_fastcgi.c.3329) response not received, request sent: 1394 on socket: unix:/tmp/php-fastcgi.socket-1 for /pkg_edit.php?xml=bandwidthd.xml&id=0, closing connectionI was going to post a question about this earlier, but now my RRD graphs seem to be updating again. I'm just missing a chunk between ~9:30am yesterday and ~7:30am this morning.
In the future, is there something that can be done to keep the process that logs RRD data running? Or notify me if it goes down?