[mrtg] data collection did not complete within interval

[Clark Kee]

Our mrtg/rrd installation, which has been running fine for months, 
recently stopped being able to produce most or all graphs. Inpection of 
the rrd files showed NaNs were being written, and the mrtg log showed 
the warning in the subject line of this message. We were running with 2 
forks. Increasing to 4 did not seem to help. We monitor a little over 
800 targets. Any suggestions as to how to deal with this, or additional 
diag info to gather welcome.

mrtg 2.16.2
rrdtool 1.3.1

Clark Kee
PINS