New Cacti User: RRDs Updated with NaN

[RoyRapoport]

I've added two new data input methods, tied to data sources, tied to graphs; the DIMs both refer to a script I wrote. For debugging purposes, the script at this point just outputs a random integer between 0 and 90. The script outputs this integer on a line with no newline/linefeed at the end.

Weirdly, rrdtool dump shows the file being updated regularly (so no permission issues, I assume), but it's updated with NaN. One data source is configured with 0/0 min/max, the other 0/90 min/max.

Clearing the poller cache worked for about three cycles, and then gave me NaNs again.

poller in debug mode gives me the handy:
3/22/2005 02:30:02 PM - CMDPHP: Poller[0] Host[0] WARNING: Result from CMD not valid. Partial Result:
03/22/2005 02:30:02 PM - CMDPHP: Poller[0] Host[0] CMD: /home/rsr/bin/towork, output: U
03/22/2005 02:30:02 PM - CMDPHP: Poller[0] Host[0] WARNING: Result from CMD not valid. Partial Result:
03/22/2005 02:30:02 PM - CMDPHP: Poller[0] Host[0] CMD: /home/rsr/bin/towork, output: U
0

I'm not sure why it doesn't like the output of /home/rsr/bin/towork; when I run it manually as the cacti user, I get valid results:
152 puppy cacti /usr/local/cacti-0.8.6c/log> /home/rsr/bin/towork
57153 puppy cacti /usr/local/cacti-0.8.6c/log>

Suggestions? Neither the FAQ nor the documentation were immediately useful.

This is on Solaris 9, BTW, with PHP 4.3.6.