[Orca-users] No data plotted reading from log ( date_source file_mtime )

[rscrane]

When I feed a file with datestamps to orca witht -once flag, I get
plots.

Same file w/o datestamp and data_source changed to "file_mtime" ,
graphs are generated w/no data points and "NAN" in all the
Min/max/aver legends
this is 2nd cfg file:
state_file              orca.state
html_dir                /export/home/c/public_html
expire_images 1
group servers {
find_files t2.log       
column_description      Active Idle
date_source file_mtime
interval 300
}
plot {
title Apache Server Processes in Use
source servers
data    Active
data    Idle
data    Idle + Active
plot_min  1
plot_max 50 
legend Requests
legend Idle Servers 
legend Sum
}
the file t2.log looks like this ( appended to every 5min):
18 8
8 9
17 6
12 5

Running on Solaris 8.  What am I missing?

TIA --